here's my .02, I wanted to keep it stock looking under the hood, but you can definitely achieve what you want power wise the cheapest with an LS swap. it's definitely more work and planning though.
if you don't want to do an LS swap, you'd be hard pressed to rebuild anything cheaper than what I got. it's a vortec long block from gm (L31-r), not rebuilt. I paid $1900 from summit, although they have it listed for $2070...I price matched. when I called local machinists, they were far more to rebuild what I had in the truck and their rebuilt long blocks were much more expensive as well. rebuilding makes sense if you can get a smoking deal on the machine work or if its a numbers matching vehicle. otherwise, it's not economically feasible.
with the l31-r vortec long block you get the benefit of the vortec head and roller setup. however, you'd still need an electric fuel pump, because the block isn't machined for a mechanical pump. you'd also need a new intake manifold for vortec heads, melonized gear for your distributor and maybe some reworking of your accessory mounts. I just bought a whole serpentine setup from craigslist for $100. I got the two brackets, accessories(water pump, power steering pump, alternator, a/c compressor, etc), oem intake manifold, oem vortec injection, oem distributor....basically everything but the long block. depending on what emissions equipment you have to run in your locality, you could end up with 260hp or much more if it's not choked down. I'm guessing you could get them to 325hp/400tq without any emissions stuff and proper carb/timing tune pretty easy.
as for the fuel pump...like others have suggested, I went with oem 87 tank and a high pressure oem pump for my efi. to run a carb setup you can do the same minus the high pressure pump. or you can frame mount an inline external pump with your current tanks. I know people will say they won't last as long, which is true, but I had a cheap inline one from Napa for years without issue. you'll likely need an inline pressure regulator too. most inline pumps put out 7-9psi. you want around 5.5 for most carbs. buy an inline fuel pressure gauge if you go this route and triple check your float adjustments.
