Inky, I can't contribute to this from a technical standpoint, as we've never tried such a swap.
But since nobody else has responded either, I CAN make a social contribution - don't worry about what anybody else thinks of your project. The purists will frown on the 350, the rodders would have done something differently, and the jerk next to you in his chopped street machine at the gas station is going to look down his nose anyway.
Have fun with your project and be proud of it! I have an old '76 K5 with a new 350 that needs a new job, so I'll be keeping an eye on your progress for ideas!
- K
