I used an ebay kit that ended up being from Mike's. Went back to them directly to get the electric choke and a couple other things. The kit was decent quality and have had no issues. If I'm not mistaken they carry the jets too, and they also have several Youtube videos in case you need a refresher on carb building. As far as jet sizes.........I pretty much left the stock jets alone and it seems to work well for me, but I'm running a basically stock reman engine for now. I've got an Xplorer GT40 motor that will be going in eventually, and it'll be a little more on the performance side, but the plan is for fuel injection at that point. I do know some of the 4100's run holley jets, just don't remember whether early or late models.