1993 Ford F150 runs good cold but when warmed up it started overheating and bogging down.

...well the waterpump may be kaput, though looks totally normal on the outside, you may even be able to wiggle the shaft, but isn't leaking out the weep hole? seen it lotsa times where the guts/fins on the pump have deteriorated to where it no longer pumps coolant very well. another complication may be a rusted water jacket, if water instead of coolant were used for any length of time would start to clobber up the coolant loop, to where controlling the temperature would be difficult-

After it had warmed up, is the top radiator hose hot? If not, you're not getting circulation through the radiator. I had a grand Torino sport in the 70's. It would do the same thing. Turned out to be the powerpack bolted onto the firewall. Engine would run like crap when it heated up. When cool, it would run fine.

You can also set the thermostat inside the vehicle to max heat and turn on the heater when the engine warms up. If the hose going to the heater core isn't hot (And I mean hot) you have a circulation problem.

or unbolt and omit the t-stat, forcing it to run 'full open' to still if it still overheating~

Turns out, I'm losing water. Is it possible to have a blown head gasket and not lose compression? It will run fine like I said for about 30-40 minutes at this point but after that it starts to stutter and bog down.

oh no say it ain't so. Look at your oilstick, hopefully it won't look like Jell0 pudding, if it does, tip off and should be taken care of right away, we really don't want coolant where oil belongs. headgasket--allright, but cracked block-NOT alright, so do your forensic analysis, as clearly you've got to stop driving this and tend to it's major problem(s).

No coolant in oil! Could it still be a head gasket?

well yes. there are only a couple of places for this boiling hot coolant to escape to, into the cylinders thru a 35 dollar headgasket or thru a crack in the block, I have seen weirdo leaks thru and into thread cavities, but always a tale of woe with loss of coolant. Got a weekend, unbolt the head (noting the positions thru holes in a soda case) pry it up and take a looksee at your gasket to see if it looks like grannies trowsers or seems like it should be holding coolant. The coolant will leave a trace where it's leaking. You should take note of how much force it takes to loosen the head bolts, because perhaps just giving them each a quarter twist may solve the problem...tooo-

Well, I've taken the heads off. Took them into the shop and the only things they came back with is 2 bad exhaust valves and 1 intake valve just a little worn on each. Seems to me that if this is the case then I'm dealing with a loss of coolant with no loss of compression. Do you think it may be a crack in the block?

I'm leaning toward going to pic a part for another motor. What do you think?

Well, you don't quite know what you're goin' ta get with a U-pull engine, I'd stray away from something like that and either get a 'crate' motor if if you are going to keep this buggy a long time go with a Jasper rebuild, sure they cost more, but every component part is either NEW or good as new, and every one of their engines is guaranteed for years...and they are painted an easily recoginized spiffy green color. ebay often has bargains what can be had for cheap, if this is your only critereon-

So cracked block? you don't want to bother with where the crack is, 'cause it is akin to putting a band-aid superhero colored strip on there to cure coronary thrombosis. oy vey- gotta wonder how did this happen? manufacturing flaw? someone ran it out of coolant one day and decided to just use a garden hose to refill it? no answer will be satisfactory...new motor is the judgement...gavel down~

If your heads are good yet (and sounds like they are) you could price out a "short block" from your local vendor...might save a bit of scratch~ You'd be saddled up with installing the headgaskets, but you know it'd be done right, following the torque table and spec~ components like a/c and p/s can simply be re-used.

Rob, my neighbor says that you have replace the heads if the seats are burned, and have been overheated, they must be replaced...from the owner of a chevy silverado 4x4 K20 camper special silverado-

If you are going to keep the truck for any length of time do not go with the pieces parts route from another motor. I would also stay away from an engine labeled as "rebuilt". A friend was in the business prior to retirement. "Rebuilt" means repaired up to the point of initial failure. Stick with an engine labeled "remanufacturered". He suggest Jasper reman. he indicated something like the warranty is 100,000 miles. You do have to shop around for the best price. He got one dropped into my explorer for 3500.

im not sure what its called but there should be a thermostat type plug in the side close to the top of the block, there will be an electrical plug plugged into it. find it and replace it. problem solved.