hey my friend just bought 1986 olds cutlass with a 307 ho with 7a heads he ask how much power can you get out of a 307 ho and is it worth building thanks for your help  

Generally no...not worth building.  I've seen some get up in the 300 HP range...but that requires quite a bit of work.

If he does decide to...absolute first thing he needs to do is ditch the 7a heads, the intake, the exhaust manifolds, and the camshaft.  The 7a heads are terrible...and Oldsmobile put intake and exhaust manifolds to fit the tiny ports on those heads.  Camshafts are just common sense...they are going to have very very low duration and lift numbers...despite being a roller camshaft.

Oh...and the computer controlled quadrajets are pretty weak as well.

The bottom end should be beefed up to handle any serious power (ie 300 HP for that engine).  

If you're still interested...here's a link from Joe Mondello's website.

http://mondellotwister.com/ArtGiantK.htm  

yea, save your money and get a olds 350 or 403, direct swap