engine not fitting in bay

[freds]

Hello, I have a 1967 Chevy pickup that I have been rebuilding, also bought a totally rebuild engine from the local automobile parts store, when I tried to install it in the engine bay I noticed its length is too short. the rubber mount on the bell housing do not reach the cross member for support of the engine by approximately 2-1/2 inches, is there such thing ???. please help.

I have a friend which removed the previous engine which we interpreted to be a 350 engine, he can't recall how the engine being held up in the bay.

Originally in this truck was a 292 cu. in line-6 engine