I think the LS7 is at the very high end of the budget, engine is 13k out of the box and I dont think that includes the ecm. Add the oil system hardware and electronics and you have to be at 15k, forget about forged internals, these engines go near 20k when done. To get an ls7 to 500 rear wheel hp gonna need a cam change as well(should be close). Im with Jody on the LS2/3 modded will be cheaper. Keep in mind the accessory drive systems for these engines aren't cheap and pipes as well. My vote is for the ls3 with a stroker crank.
Also has to be 100+ pound difference off the nose of the car comparing the LS to the ramjet.
Rich