I recently installed a newer motor in by Bros sled it is out of a 1999 Indy 500 his was a 1990. Now what I came across was that this new motor he got came with the original carbs, and they have 340 mains in the original motor he was running 280 mains. Now I thought that they are identical motors and I would say should run the same jetting. This newer motor came from the same area so elevation and temp are not an issue as to the different main jet sizes. And they are both VM38 mm carbs?