Go to Pull-A-Part and pick up a Vortec long block on a discount day. Get a pair of spare Vortec heads just in case. The odds are pretty good that at least two of your heads will be cracked. Have the block, heads, and crank vatted and magnafluxed. Reuse the stock rods and pistons, but put new rings and bearings in the short block. Do a mild port on the heads. Get a set of stock LS2 beehive valvesprings, a set of Comp Cams 787-16 retainers, and some umbrella valve seals. Call your favorite cam company and let them know you can run up to .530" lift and get a cam that suits your purpose. You should be in under a grand, and the NV3500 was used in the 1500s behind V8s, so with your lighter weight you should be fine.