I am running a 270 bored to 292 in my 50 GMC with an Oregon Cam Grinders Cam (after Delta in Tacoma screwed up two cams) and flat top pistons with dual Nicson intake and exhaust . . . A833 OD tranny with 4-on-the-tree and 12 bolt posi @ 3.73 from a 69 C10 out back. It is a sweet setup and has no problem keeping up with traffic. Lots of build info on oldgmctruck.com
The closest original GMC engine color I have found is Ford red Duplicolor DE1605
I have lots of engine parts for 228, 248, 270, and 302 inlines along with a number of decent complete engines.
These guys are local to me and do great work.
https://www.oregoncamshaft.com/ I used larger small block valves and big port intake with runner adapters, modified S10 HEI ignition and full flow oil filter. Also adapted a dual chamber master cylinder . . . a fun project that kept me busy for a couple of years of weekends and some evenings.
