There are quite a few web sites out there with information on the various Pontiac cylinder heads. Google "Pontiac cylinder head codes" to find a bunch of them. Just about any d-port head with an appropriate chamber volume will be a good starting point as all the ports are pretty much the same. If you're on a budget the trick is to find some heads that don't need a bunch of work/machining. In general, aim for a set of heads that already have the "large valves" (2.11 intake, 1.77 exhaust) and screw-in rocker studs (with pushrod guide plates) as opposed to pressed in rocker studs. Heads can be modified to have both those features but why spend money for parts and machining if you don't have to? The one aspect that's not easily modified is the combustion chamber shape and size, so that should figure significantly in your selection criteria.
Also, learn how to cc heads yourself. It's not hard. I used a flat piece of plexiglas, some grease, a large plastic graduated syringe, and colored windsheild washer fluid. I measured every chamber 3 or 4 times and averaged all the results to ensure I was getting accurate measurements. It's important because just a couple of cc's makes a difference in compression ratio, and Pontiac heads are known to vary a lot from the published factory chamber sizes. This is an area where you want to be positive you know where you stand.
If you have Excel available, I have a spreadsheet I can send you that does all the calculations necessary for compression ratio --- there are also web sites out there that can do it too. For a +0.030 455, assuming "standard" head gasket compressed thickness of 0.042 and a "usual" piston deck clearance of 0.020, a total clearance volume of 114 cc's will put you at about 9.3:1 - a good spot for iron heads. Making up that 114 cc's are 4.5 cc's from deck clearance, 9.45 cc's from head gasket, 6 cc's in the flat top piston valve pockets, and 94 cc's in the chambers. Zero-deck the block and you lose 4.5 cc's, upping compression to 9.65:1 - so you'd need to get those 4.5 cc's "back" from somewhere (like dishing the pistons, using a different head with 98.5 cc chambers, or using (much) thicker head gaskets. Using thick gaskets though is going to effectively eliminate the very beneficial cylinder "quench area" so that's not a preferred choice. That's why having a tool to work with compression ratios is nice. It lets you see the effects of various changes and parts combinations easily before you start putting out the cash.