Hey Nova Deuce,
Get used to hearing the "Put a V-8 in it" that's the standard line and would be a simple answer, but Small Block Chevy's are like Belly Buttons . . .EVERYBODY's got one ! I'm at the same point as you only with a '69 Camaro project. It's far from my first build though, this is may second Camaro and I've done almost 20 cars total, mostly Chevelles and El Camino's. All had V-8's so this time I decided it's time for something different.
My suggestion, build the six and if for some reason your just not happy with it the V-8 swap into your vehicle would be simple. Of course the guys here would hunt you down and Duct tape you to a tree or something if you did, I'm sure !
It seems that the standard proceedure for any inline six project is to start by buying Leo Santucci's book about building the inline 6. Do a quick search by his name and it's easy to find. I think it's available through this site also.
Your car looks like a great project I hope to build a '66 or '67 Nova some day. They're on my list of "want-ta-haves" You've found the right site for the info you need. Just start pouring over the old topics and you'll get most the info you need without even asking any questins.
Good luck on your build. . .
'Crockett