i have a couple of questions as im about to do a ls1 swap 1. are the pistons , crank interchangeable? 2. do i have to splice into the main harness in the car or is it a complete bolt in 3.will my 700r4 fit? these are general questions as i dont know which year ls1 yet

Do you mean L98 and LSx crank/pistons interchangeable? Not even close.

See the sticky in the top section of this forum for info about the transmission and wiring questions.

There are very few things useable from the L98 directly. The radiator and radiator fans are about it (and you will have to rewire the fans).

Just judging by your questions, you REALLY need to spend some time doing some research (not trying to be mean). Check the stickies, and check the current swap threads. I promise you that those questions, as well as almost any other questions you might have, are answered. Both here and over on LS1tech. The year of the LS1 doesnt matter for the questions you asked. The basic swap guidelines hold true for all of the LS series motors.

J.