Nice Vette man, my mom has a 60 red w/ white insert and original 283. With your problem of a too small intercooler, check into helping it with somthing cold. Water sprayer or a nitrous/CO2 spray kit. They will drop your temperatures, safe for motor and I/C, and keep from re-fabricating uner the hood. I own a sport compact and alot of guys are runnin that w/ their cars and getting some good numbers. If you want more info on them look at some WRX forums, there is a bunch of literature about it there. Also, could you make a under car scoop for it like the GN's had? I made and extention that sits about 2 1/2 inches below the car to grab more air, if you have room it would help. The dutweller neck would also be a world of help in that tight space. Back to Japan, if you check out Blitz (I/C company) they might have a more efficent small I/C than our 16 year old ones. Also Ramchargers have some stock location I/C's, but I don't know the diemensons. I know the height problems under the C1 hoods, Good Luck.
Nick