I've running at Bonneville since 1975 setting many records all using vintage engines. Can't tell what to build but the best analogy I ever heard was to build it like you were going to off shore boat race it. No one I know ever did it with a GMC 6 so I was on my own. The biggest suggestion I can give is you cannot have enough compression. I run my Jimmy's at 14-1 and wish I had a little more. Blowers make compression so look to the supercharged classes. If your going to run fuel get the biggest mag you can. If your going build your own car you'll be in $10K for safety and required stuff.If your serious go to SCTA-BNI.org and get a rule book. The biggest thing is to forget ANYTHING you have ever learned from any other racing venue. An Indy car could never be made to be legal and 99% of the NHRA stuff won't make it either.
The USFRA has a 130 MPH and 150 MPH club so you can have some fun with your street car but the to the SCTA everything is a race car and must pass inspection.......Good Luck
PS: Running 216 in an open roadster with 75% in the tank is a lot of fun................JD