Good thought about offset grinding the crank. It certainly wouldn't hurt to pick up any extra cubes on the little motor. I'd seen a couple of NOS 283 standard cranks still crated, if I was lucky enough to get one of those it would be nice to not disturb the tuftrided bearing surfaces. But if I get one I need to grind offsetting the throw is something I'll consider.
I believe the 400 pistons are 1.56' comp heights and 327 are 1.675, 302 are 1.80 and 383 for the 5.7 rod are 1.425. I'm not sure about 350 pistons, I haven't built a 350 since I blew my last couple of them in 1980. I've stuck with shorter stroke motors since then, just personal preference. I know the figures for the comp heights ar from Chevy and they do vary some. The thing I think I'll do is put it together and see how it mics out and decide what needs to be done. I thought about milling the pistons, but it's a little tricky unless you're running flat tops.
I'd wanted to build a short stroke, long rod 400, but after another round of bad news from our company, I've decided to just work with the small journal block I've got on the stand right now.