That'll be a 532 right?
What crank/rods/pistons? Long rods absolutely help, there isn't much downside as long as you can fit the rings on the piston.
That should be a lot of fun, and a bigblock at 7k sure sounds nice. Your truck is reasonably light, so something with that size bore and only the stroke of a 454
ought to move you well enough.
Any ideas on heads/cams?