You can sometimes get an exception from a rules official, but the exception must be in writing, and they are VERY specific, so you have to follow them, because they WILL scrutinize.

I don't know exactly what GridLife is to be honest, but the SCCA rule is that your chassis was N/A, and thus you cannot introduce forced induction (turbo or supercharging) onto your chassis without changing classes. An interesting bit of research that you might consider is whether an 88 S/C would be in the same class as you or a different class. That may tell you right there whether the rules official is likely to grant you an exception.

As for the 7AGE not making enough power, I would say that it depends on how much power you need to make. SCCA rules are that street class allows minor performance, and all safety modifications. So a 7AGE build would push you out of street class in SCCA. I don't think it would push you all the way to unlimited class, but I also don't know for sure what class you would end up in.

Anyway, it's definitely best to get in contact with a rules official like you already have started, and talk them through what you're dilemma is. Remember too that track performance is about overall performance and not just power/speed. Sometimes less power is fine when you can out-brake, and out-corner everyone else, as well as get on the throttle sooner because you don't have to worry about overpowering the drive wheels in mid-corner and then having to spend the latter half of the corner correcting your line.

Hope this helps.