Cost varies dramatically for different reasons; for example I picked up the Engine and Tranny for about $2,800 no accessories. The engine had 22,000 kms and the Tranny was a fresh rebuild from the states. I paid more for low mileage. Ideally you would want a complete pull out from the ls based car of your choice. This lets you bypass all the little costs of sourcing and paying for accessories like alternator, water pump, etc. The swap does not require shallow accessory drive from the vette, the accessories from an F-Body car are more ideal. As you can imagine there are quite a lot of variables. I would peg the average cost at about 9G's as a DIY (Assuming your labour is free), more if it is from a shop. If you are serious about it give Auto Evolution a call Rob should have an excellent idea as to how much he would charge to do it again.
You can retain the A/C. I did not have it before the swap; but it will be back in before next summer. I was able to keep the brake booster, although it sits very close to the head. Everything inside the car, with exception of items related to fuel mileage, continues to work after the swap.
Rich thanks for the offer but 3.15 is the wrong way. If I really want to feel the torque I would go to 3.46 or 4.10. for now I need some kind of decent fuel mileage. With the 3.23 I can cruise all day in 5th at 120 kmh pulling 2000 RPM. You will see what I mean tomorrow.