We can't give a blanket ruling on a car from another series--all we care about is whether or not it passes our tech.
That said, cars built to SCCA or NASA roadracing specs (pretty uncommon in a $500 race), tend to do just fine in Lemons tech. Cars built to circle-track specs (not surprisingly, pretty common in a $500 race) tend to do very badly (with the exception of NASCAR stuff which tends to be hella beefy).
At Buttonwillow, the inspectors drilled the cage of an ex-circle track car (ironically, an Escort), and found the wall thickness of the tubing to be insufficient. $1400 and one overnight custom cage later, they were in the race....
Bottom line, if you are buying a car with a cage, it's up to you to apply the same if not higher scrutiny as our tech inspectors will. If you don't have the expertise to properly evaluate it, it might be a better idea to start from scratch--at least that way you know what you've got.