How to reinforce a rusty BMW jack point?

^Thanks for this; that's a great suggestion, but welding is beyond my demonstrated skill set right now (How hard could it be?), though my company has an educational benefit which will pay for a welding certification class I hope to take in the next month or two (/or CDL "A" training - I can pick one).

I'll get pics shortly, but quickly: the driver's side rear block is there, but the r.r. side block area is gone - crumbly.

Looks like the r.r. side can be jacked using the floor pan area?

Can I use spray foam in the opening for support with a board on the outside?

I've previously read about welding jack points to underneath cage mounting points - I'm planning on that later. This is initially just to replace the brake line so I can drive it on the road for a short time before starting a build (if I choose this candidate).

... Ok, I think I've just answered my question about spray foam - pretty sure I don't want to be melting it while welding in a cage.

Detail:
I have a jack stand under the l.r. lower control arm, but I'm not confident in it beyond getting the body up just high enough to look under with the wheel and tire still on. The arm has a compound curve that I don't like for a jack stand support, so I'm not counting on it. The jack is still on the lifting block, and I also have an oak 4x6 under the tire.

It's the r.r. I'm mainly concerned about for this question.

I'm planning on building cribbing before going under (i saw that suggestion before as well). And, this is outside on gravel, dirt, and no cover. And a slight incline.

Brake line replacement is a lot easier on full- size vans, that's for sure. Plenty of room underneath while on the ground.

If you have never done a cage, or have limited welding skills take it and have it done. The last thing you want to do is show up at a race, after spending time and money and fail tech.

This is a great idea... I should really do this. Seems like a better alternative to waiting for our pinch welds to stop bending (they just keep on going and going! lol)

Kinda. I didn't continue the cage tubes through or anything, but I did place the new points in the same area that the cage lands, so the new spreader plates are welded in on the other side from where the cage spreader plates are. That's about as tied in as I could get. I also made sure that the spreader plates for the jack points wrapped down around the main chassis rails of the car (as much as a unibody car has chassis rails, but the main box sections that run fore and aft). I put in a LOT of spreader plate so I could have it grab onto and spread the load as much as possible.

It did work well. I put the car on the lift after putting in the new jack points, and got lazy adjusting the pad heights on the lift arms. Normally when I don't get them 100% even the car just twists a little and compensates (talking like 1/4-1/2 inch off, not inches). The E36 lifted on 3 points... didn't twist at all. Felt good about that one.

Wholly Crap! Those stands make me nervous just looking at them. No lateral structure to the stands other than the top weld for the pin? And meant for 'uneven ground like we get with Rally cars'?

Thank you, no, not me - I won't be on their crew.

I think you're smart, not lazy.

Now, the 'pin receiver' function on the car - that's interesting.

As is, they'd have to prove to me EACH stand is capable of supporting the entire car balanced on the end of the pin without deformation, like putting it in a fixture in a press and and hitting it with the weight of the car. And they don't look like they'd survive that Q.A. test.

Though I _could_ be wrong...

Now, a reinforced top with a lateral component to each stand, such as a (minimum) triangular base space frame, would give me a lot more confidence they actually cared about crew safety rather than "How many can we easily put in the truck, while taking up as little space as possible?"

For that matter, regularly available, commercial-built jack stand with a 'pin' modification to the arm wouldn't be hard; might even be able to make a 'swivel-to-lock' function work safely depending on the strength of the pin - and the 'lock' function.

Rally style pin stands are fine, so long as the car is designed for them. They're fine laterally because they use a fairly long Pin into a close fit tube in the car's rocker, often integrated into the cage. That holds the stands vertical with no real risk of collapsing sideways. They also shouldn't really rock forward/backward because the bases are wide enough. As long as you build the stands correctly they are plenty strong. In fact this style stand is actually how the BMW road side jack works on most cars, or did, I'm not sure if/when they changed it. But the E36 has plugs you remove from the side of the rockers, then the jack inserts a pin horizontally like those stands, and you lift (assuming they aren't rusted out).

My comments on flexing on the lift were just about chassis stiffness. Normal car when you don't have all 4 pads 100% level with each other the chassis will twist a little when lifting and all 4 points touch and support. My E36 didn't flex at all and left one pad just floating. I put it right back down and adjusted the pads better.

That has to have already been done to death, hasn't it?

I mean, Ok, I support the idea that an old, stale joke that someone references over and over again can become funny again [ex.: "Badges? ..."]; but that's really about the subsequent repetition, not the old joke anymore (my life is full of these already).

But I can't imagine this idea has yet gotten to that point; I don't think it's old enough. I can only imagine it's in that interim stage, where even those who repeat it admit it's just sad, and tired, and unimaginative.

... but: if it hasn't been done that many times, in the east, yet; ... agreed - that's a brilliant idea.