[Brad54]

Here's my list, and reasons:

'60-'62 is more expensive, because they have the torsion-bar front suspension, X-member frame and hydraulic clutch. All of these things combine to make parts for a rebuild and upgrade more expensive. The parts ARE out there, but you'll pay a higher price than later trucks.

'60-'63 has the wrap-around front windshield, which I REALLY like. Windshield is much more expensive than the later trucks, as are the vent windows.
They have the drop-out center section rear axle assembly, which is expensive to rebuild, and limits your gear choices VERY much.
An optional Dana 44 rear axle was available for these years, and while they're a fantastic rear end, have about 20 different gear ratios available, and are still used in Fords and Jeeps so posi units are cheap, they're very rare to find in the '60-62 truck mounting points.

1963 has easy and inexpensive mechanical clutch linkage, essentially the same frame as later trucks, and is in my opinion the best of both worlds: the later style frame is easily upgradeable with more modern front suspension, and it has the cool wrap-around windshield.
The rear axle is a bit of a one-year-only deal, but not a deal-breaker.

1960-61 trucks, if you like the big Double Bubble hoods, those are expensive.
The grilles for 60-62 are also more expensive then their '63-up counterparts. Both to buy, and then to rebuild since for '60-'61 you've got to buy twice the number of lights and adjuster hardware.

Factory full-instrument clusters are more expensive for the '60-'63 truck as well.

'64-'66 are the easiest and cheapest chassis/suspensions to upgrade of the era, with factory junkyard parts from later vehicles, and after-market parts.
The windshields are much cheaper than the wrap-around earlier ones.
Full-instrument gauge clusters are cheaper if you want to upgrade.

Just about EVERYTHING is available reproduction for them, while there's a lot of holes in the '60-'62 offerings.

All these trucks are still found in junkyards, but it's not like it was 10 years ago.

Factory options like Power Steering and A/C are nearly non-existent, and expensive when you find them, power brakes are rare too, but the aftermarket has that covered.

'67-'72 trucks are very plentiful, everything is available for them, they had more factory options like A/C, Power Steering, Power Brakes, factory sway bars, disc brakes on the later ones, they're plentiful in junk yards if you like junk yard crawling (I do), and the aftermarket is choked with everything you'd need. And it's usually cheaper than the '60-'66 stuff.

Me? I like the '60-'63 trucks, and that's what I've got (Suburban and K10).
If I was starting from scratch like you are, I'd go for the '63-'66 trucks.
If I was strictly going by cost, it'd be '64-'66 trucks for the last of the Atomic Era, but '67-'72 is better strictly from an accounting bottom-line perspective.

The '55-'59 trucks look great, but they're about twice as expensive to build as the '60-'66 trucks, starting with the purchase price and going from there.
I've got a friend who loves them, and he keeps buying starting points... a ROUGH, non-running starting point is $3-4K, while I can buy complete, driving '60-'66 trucks all day long for that price.
And then buying the parts needed to get the '55-'59 trucks back on the road is much more expensive. For cabs that aren't as roomy as the '60-'66.

For powering yours: Crate 350, 290-350hp is all you'll need, they're cheap, reliable and have a warranty. Brackets, intakes, power steering conversions, and everything else you'll need is a lot cheaper than building and dressing an Inline 6.
Overdrive trans, with 3.55 or 3.42 gears in the back will honk you down the road at 75mph all day every day.

Get a good radiator, a factory fan shroud, and the biggest fan you can fit in the opening.

-Brad