I have a 1954 GMC 350 dump/flatbed with original 270. The exhaust manifold fits poorly; leaks with one combined intake port on cyls 2 & 3, and out exhaust port#4 despite new gasket & retorque @ 20ft-lbs middle studs and 30ft-lbs on outer studs. Is the manifold or head warped?

In the same vein, I have access to a rebuilt Chev 292 which is in near perfect shape, and with much less worn 4sp transmission. How hard would it be to fit this engine in the old GMC?

Thanks!