have a question about an engine swap.putting a 6 cylinder in my 54 chevy bel-air.I have a 75 250 chevy with electronic hei ignition also have a 250 from a 65 chevy.any suggestions as to which engine to use? are there any differences in these motors?is one better than the other.any info would help.Thank you in advance.

are you sure that "250" in the 65 isn't a 230?

If that 65 is a NOVA you most likely have a 230 not a 250 Unless someone had changed it. But with that 75 you may want to change the head. If yu plain on useing any type of aftermarket intake system.