Just be realistic about the expectations you have for your engine. Ask yourself what you want from it and stick to it. If you want a bit more punch from it and for it to be reliable then stick to the above mods, although an oval port H89 head would be as good or better than a ported A12 round port head. You don't need a GX head, although nice, you won't be able to find one for under $500 that isn't missing at least 5mm off the face from the speedway guys. Unless someone generous is willing to part with one at a reasonable price.

the above mods can cost up to $2K easy depending on how you go about it. I just bought a decent 23/36 manual choke weber for $100 the got it rebuilt properly for $220. Adaptor new $44. Extractors new $350. Exhaust $250. Camshaft and lifter grind $120. It is the trivial things that will catch up with you.

It doesn't really matter what you do with it, you will be bored with it in about 4 days anyway!!