1.) should i replace head bolts?
Are they corroded? Bent? Twisted?
IF (big IF) they look good...re-use them. If they're damaged, get new ones. There's nothing wrong with the GM bolts if they're in good condition.
2.) what are the best head gaskets to use?
How far below deck are your pistons? Typical is approx. .025. The engine was designed around .020-thick steel shim gaskets which went out-of-style when Fido was a pup. Anything thicker than .020 head gaskets increases the quench/squish distance, reducing turbulence in the cylinder. This makes for a slower, lazy burn needing excessive spark advance, and THAT leads to detonation.
GM and the aftermarket have .028 compressed-thickness head gaskets, I would not use anything thicker than that. "Ordinary" composition head gaskets are typically .040 thick.
3.) should i pull other head and do gasket as well?
I probably would. Depending on mileage and wear, you're probably looking at a valve-job with guide work anyway. You'd know for sure when the first head gets cleaned and inspected. Once the valve springs are off, it'll be easy enough for someone to rattle the valves in the guides, look at the valve faces and valve seats, and generally inspect the heads for wear.
You're gonna pull the springs off to replace the valve stem seals anyway.
4.) anything else i should replace while i have easy access too?
If that were mine, I'd shitcan the flat-tappet camshaft and lifters in favor of an OEM-style roller cam, the thrust plate, timing chain 'n' sprockets, roller lifters, dogbone, spider, shorter pushrods, and have a good look at the rocker arms, 'cause there's about a 50/50 chance they're totaled, too.
Be sure the gear on the bottom of the distributor is in good condition.
All the roller-cam parts can come from a Treasure Yard short-block except--maybe--the timing chain and sprockets, and the thrust plate (which come as a kit from ACDelco) When it was me, I pulled the used lifters apart one-at-a-time to clean and inspect them. Or buy a hardware kit that has the dogbones 'n' spider, a cam, and the timing set with the thrust plates and bolts. There's more than one way to get the roller-cam hardware to install in your block.
So this is a TBI engine? The swirl-port heads are not much for performance. I get the sense you don't want to replace them, though. I suffered-through swirl-port heads on my K1500 for a couple of decades; they work but they don't make power. Last time the engine had to be re-done, I got rid of the swirl-ports in favor of aftermarket aluminum heads. You'd be looking at another thousand+ dollars--minus whatever you DON'T spend fixing the heads you've got. I'd rather have QUALITY aluminum heads than valve-jobbed swirl-ports.