I pretty sure its both stroke and bore to get 42x... a ls1/6 block can be resleaved to get the bore necessary, and the rest comes from stroke..

C5R block is made from day one to have the big bore, plus its stronger.. and alot more expensive.

 

You can stroke a LS1 to about 4.25 stroke. The aluminum LS1 cant be bored over more then 3.905. If you want to go big for cheaper, and dont mind a weight gain, go with the iron truck LS1 block. They come with a 4" bore and can go .60 over and can take a stroke to 4.25. Plus you also get a stronger block.

 

A 388 All bore motor is easily acheived. It's only a 4.125 bore, resleeved of course. A 382 is only 4.100 inches. That's about the largest you can get on the bore side, maybe slightly more for NA only applications. In all cases you are looking at a resleeved block which will run up to 3k alone depending on who you go with. That's sleeves and labor.

As far as stock over boring I think you only end up with something around 360 CI, but I'm not sure. If you offset grind the stock crank you can get up to 392/396 cubic inches with an all bore mini stroker. Black Sunshine/ 00SS (Harold) just got his done like this.

As far as a 427 goes, it's roughly a 4.125 bore on a 4" stroke. You can mix up the dimensions a little depending on a few things, but that's the rough setup. It requires a new crank, rods, pistons, sleeves, etc.

 

whats a estimate for a 383 stroker kit installed?

whats an estimate for a 382 bore?