olds 307 and 403

I am pulled the Olds 350/2004R combo out of my 88 Cutlass and was going to put in an Olds 260/TH350 that is starting to slip to keep it mobile. There is a 1974 455/TH400 out of a Delta 88 an hour away for $500. The only issues I can see is piecing together a Qjet as the original was thrown out, I would match it closely to 75/76 455 specs, mine being an 800 cfm version, maybe +1 on primary jetting. I am wondering how close the Sanderson headers would have a chance of fitting? I have a complete 2.5" exhaust on the car. I am thinking possible steering shaft interference and maybe the frame since it moves it out further and higher, correct? Does anyone know how much lower G body Olds V8 mounts sits compared to earlier mounts? Do the frame mounts have to match the engine mounts on 70's and up cars? I know they had to be matched on earlier cars. I am running the taller mounts with my SBO, every clears OK. The heater box and hood are no issue. The heater box is damaged and I have a hood scoop. I know I would need a different yoke and my driveshaft shortened. Everything but the carb looks to be included, even trans lines but the exhaust manifolds are cracked and carb gone. Am I missing anything? Thanks.