Don't be too hard on your self for the sbc decision. Dollar for dollar the Chevy is more bang for the buck. Especially when you are starting from scratch. I've had almost every Olds engine in a G body Cutlass. 260, 330, 403, 425 and 455. That was back in the 90's when every junk yard had plenty of them at realistic prices. Now 25 years later those engines have either been sitting since then in those same yards or have been on the road racking up even more mileage and wear and the prices have quadrupled. $375 in 1996 for a complete 455 with all accessories and now they want $1200. Hell back then nobody wanted the Olds engines, G bodies with an Olds 350 or 403 sold for much less than a similar car with a chromed SBC...
I put a GM 350 crate engine in my current Cutlass and have no regrets.