After a few more races here is where we stand.
We weighted the cost of rebuild kits for the 4R70W against the cost against swapping in a T45 along with the fun factor and went with the T45. The transmission went into the car smoothly didn't even have to modify the trans crossmember, even the exhaust cleared everything. We had to take roughly 1" out of the drive shaft. The most difficult part was grafting the mustang cable clutch pedal onto the cougar brake pedal assembly and snaking the cable around the massive brake booster. The idol air controller was then removed (computer can no longer control rpm) and the PRNDL position sensor was permanently put into P. We then left the speed sensor disconnected so the computer wouldn't pull timing at 110mph + This swap really woke the car up. Being able to select a gear and control rpm helped greatly to get the car to corner. You can actually steer it with the throttle now. All and all the manual swap cost us the same as a full rebuild kit and was way cheaper than having a transmission shop rebuilt the automatic. The downside has been we spend more time at higher rpm and have reduced our fuel runs from 3hr to 2hr.
The car weighs 3200lb wet, no driver. Like others have said we have removed everything easy and don't have much left to remove/replace without getting cheaty.
We are still running the factory 4 wheel disc brakes with the ST-43 pads. We always have more brake than tire.
Still looking for a tire that we like/like paying for. (Factory 16" rims)
We took everyone's recommendations about focusing on the rear to get the front to bite. We found that 2015 RAM 2500 front springs are the correct dia to fit the rear Not sure what the spring rate ended up being after we cut them down, but it is now much stiffer and handling has improved.
We haven't strayed from the factory 3.27 ratio open diff.
Remaining Questions:
1: Strut Rod Bushings to Lower Arm - ours we shot, we replaced with Moog after 8 hours they had mushroomed and exploded, researched the issue everyone recommends OEM replacement for this reason. We can not find any OEM bushing to buy. We have using corded rubber hose lubricated with never-seize to fabricate our own which we replace every race. Has anyone found/fabricated a more permanent fix for this?
2: Those that have recommended the PI head swap. Does the computer need to be programmed to take advantage of this? We are rather illiterate when it comes to tinkering with the ECU. We would love to get in touch with someone who knows what they are doing in this department.
3: What is the easiest way to change the bolt pattern from 5x108mm to ANYTHING other than 5x108mm.... What an annoying bolt pattern.
#814, Nothin's Hotter Than A Cougar Racing, 1996 Mercury Cougar XR7