So I been curious. What all is required to swap out a 150 for a 165HC? What changes need to be done as far as motor mounts etc? If I were to do an engine upgrade this would be it because I can't afford to put a Lycoming or anything else in. I was thinking this would be pretty much a straight swap without having to change a lot of parts but correct me if I'm wrong. I know probably the hardest part is finding a good 165HC. I also have to be able to burn mogas. I'm fed up with 100LL prices.

Bigger fuel lines other than that should be 108-2 --not sure about straight 108 or -1 . Don't think you will find any 108 or -1 with 165 hp unless it's been modified .

Oh ok. I forgot to mention that I have the straight 108.

Technically not a difficult switch. 165 will fit right into the 150 mount. To be legal you need the 1/2 inch fuel lines from the tanks to the fuel selector, which also has to be 1/2 inch. The original brass ones are not easy to find. Univair has a selector for abour 350 dollars, but you are limited to 165 hp. You can't put a larger engine in if you decide to in the future. Not a problem with the brass one. You need to replace the gascolator on the firewall with 1/2 fittings also.
You are required to put in a rudder bungee system also. The last price I saw from Univair was $2000. This has been skipped with a 337 by some guys. Yahoo has a forum for this and is a great resource.
I replaced my 150 with a 165 and the performance improvement was surprising