Before you get rid of ther original block I think I would change the motor and keep the o.e. block and ask around to see if there is a poss. fix for this with today's tech. I 'm sure someone has run across this nefore and has a fix for it.

Keeping the o.e. block to put in later would make the car worth alot more $$

I think I would call Butler or Kauffman and ask them.