I don't think you can buy an LS1 or most other newer style GM engines from Summit or Jegs. Buying one new from GM is something like $7,000 plus you may need to set up all of the wiring, computer, and sensors... I would definately recommend getting a used engine with as low miles as possible. If it is in good shape, you can drive with it for a few years before you decide to rebuild. Also, from what I've read about the LS1 swap, you may have to cut up the subframe a bit to allow for mounting the accessories... basically, I think it would probably take more than a week unless you're really working full time on this.
The ZZ3 is a great over-the-counter engine. With a few parts swaps, you've got an engine putting out more power than the LS1 in stock form for a lot less money.
If you want to go with the LS1 engine for the cool factor though, I understand. I think that working with what you've got will save you a lot of money though.
- '68 Chevy Camaro (sort of done, but always subject to improvement)
- '63 Pontiac Tempest (work in progress)
- '72 Datsun 240-Z (back-burner for now)