Heres a few numbers that i have used and then ill give ya my favorite one or 2.Ill also give ya the venturi bore.Youll want around 10-11mm.
WT579-9.53mm
WT230-9.53mm
WT500/WT548/-same carb 9.53
WT289/11.11mm-570/11.13mm-[WT600-628-33111.11mm]
I would personally go with the WT600Has a nice long shaft and hook for the choke and has the large triangle shaped throttle arm so you can easily use a ball link or clevis.Its 2 needle as all of these listed are.I was looking at what i have left for carbs and dont remember the other numbers as i sold them on engines.I believe the 600 goes for $12-14 at
ecedwards_tools-on ebay.You could do your own checking around for the others if ya want.Might find a better deal.Ive been getting around 68-7200 average with anything from 16x8 up to 17x8.I live at 3000msl.I bought 2 boxes off of the guy on ebay and every engine had different readings even with the same props.You want a prop that puts out good thrust,not just good rpms.I would stay down around 16x8 to break in first.