i have 29 with exaust would it be worth getting a carb kit for it or just save my money and what kind of power gain would i get from it its on a longtail

I wouldn't bother with it. If you want to do a lil something, have your heads done. Your probably bout due for a good valve job anyway. It's a lot less money and fixes something that likely needs to be fixed anyway. I wouldn't waste 700 bucks on a carb kit for a longtail, but that's just me.

A valve job would be the best route. I just had new heads put on my 36. You could see daylight around ~70% of one of the intake valves. My motor only had 45 hours on it. Apparently, Briggs doesn't seat the valves, they just assemble the heads and bolt them on.

Its the same block as a 35, see if the folks with blown motors will sell you the crank,get the stock pistons/c-rods from people that have replaced theirs, stock carbs and intakes from folks that have modded, etc... You can get 6HP for probably less than $700.

If I buy a bigger block, its not likely to be a briggs

the cam should be diff too correct?

The short stroke 29,31,and 32 responde really well to mods. My favorite till my Generac was a 31HP modded out.