^^ Ah, I misread your statement. I interpreted 1g 4-bolt to mean 4-bolt in a 1g not 4-bolt out of a 1g...my bad.
In any event. The reason I'm aiming for SP is that they lifted the boost control restriction as well as the fuel cut restriction. As such, anything you can do with a 14b - provided that you use traditional fuels and don't port it - is golden. So what used to be a 175whp class for us is now a 275whp class. The only restriction that remains really is that we can't hack the bumper for installing an FMIC. But with my A2W intercooler it doesn't matter cause the front core can be slim and sit behind the OEM bumper.
Now back to the rear diff issue.
15.1.C clearly says that "Equipment and/or specifications may be exchanged between different years and models of a vehicle if (a) the item is standard on the year/model from which it was taken, and (b) the years/ models are listed on the same line of Appendix A (Street Pre-pared Classes)." Since the Galant is listed on it's own line with the descriptor "all" next to it, I can put any diff from any Galant that will fit without modification but I cannot use a diff from any other car w/o being pushed into SM. Incidentally, this is also the rule that allows us to ditch ABS (instead of just unplugging it) and pull the 4ws system. Basically it's a cross compatibility with the ggsx which has the same braking system and rear subframe but has neither of the afor-mentioned systems.
The only allowance for differentials comes from 15.10.R which states that "Limited slip differentials are permitted. This permits locked differ-entials, either by design, welding, or mechanical means. Differ-ential cases, internal differential parts, and axle stubs may be machined as required for clearance and installation to the extent that material may only be removed, not added, and the exterior of the case may not be altered in any way. This machining may serve no other purpose."
Which is where I come to swapping the 4-bolt guts into a 3-bolt housing from either my gvr-4 or else a ggsx. And since (I believe) the housings from a ggsx 3-bolt and a 1ga 3-bolt are identically cast, I think I'll use one of those instead as their easier to come by and ostensibly the same once the guts have been pulled out.
Now, to be perfectly honest I'll never be nationally competitive in this car so I could probably just run a 4-bolt and nobody would ever know or care. And since it's more preventative maintenance than anything I wouldn't feel too bad about it really. Unlike a 16g vs. 14b which would fool most judges but gain me a nice little power boost. That I'd feel bad about.