Using an 18x8 or a 20x6 prop might be a good starting point. Regarding what oil and ratios to use, this topic has been beaten to death several times over right here on this forum, so doing a search should turn up all the info you could ever want.

However, most everyone has a preferred brand and ratio that seems to work best for them, but just in case you need an answer right NOW, what I will say is that any good quality 2 stroke synthetic oil mixed with 87 octane gasoline as per the manufacturers recommendations of between a 32 - 50: 1 ratio will get the job done quite nicely.

Just a reminder, gas models need gas compatible fuel tubing and tank stoppers such as the Hayes tubing and Dubro stopper. Felt filtered clunks are also a very effective way of ensuring that clean fuel reaches the carb.

Karol