Best bet is a 38DGES. It's a more modern design Weber carb and has the potential to make more HP. Make sure it's a legit Weber. There are vendors on eBay that sell them but stay away from Weber Carbs Direct. They can be shady and sell Chinese made copies. A list of companies that resell Webers -

http://www.mightyram50.net/vbulletin...!!!!!!!!/page1

If you are on eBay and are looking at Webers make sure the carb doesn't look like it's made from a blue passivated looking alloy, and it has 'Weber' physically cast onto the carb body and/or the accelerator pump housing. Fakes either have no name on them, or it's been dye printed on or a self adhesive label with Weber printed on it. They are GARBAGE