Lots of things to consider/be aware of.

When you say "primary", that imposes a lot of limits that don't favor the flathead. And I'm not an anti-flathead guy, just a realist.

First thing is there's at least a 50% chance that the block has/had cracks. If they can/were repair correctly that's not a disaster, but it has to be done right which = $. If it was rebuilt in '72 there's a good chance it was done "quick n' dirty" since that engine was very out of favor at that time. Or, in the hands of a devout restorer it may have been done correctly. Either way, if you didn't do it yourself, or supervise it personally, you really have no idea. How much of a gambler are you? Quick story. A buddy bought a very well restored '40 Ford a short while back. Supposedly everything was done, and done correctly. As it turns out the cosmetics were excellent, the engine ran well when he got it. After not very many miles it started to make a knocking noise. Kept getting worse. Once torn down it was learned that lots of new parts were put in a block that was loaded with small cracks (a common Ford flathead trait) that were either undetected, ignored, or who knows what. The block was junk.

Flatheads are also prone to overheating, again in part because of those cracks. But also, flathead rebuilders have learned that Ford wasn't real good about getting all the core sand out of the block cavities. It's not an easy thing to do, and not usually visible, so often in a "run of the mill" rebuild, it wasn't dealt with. In their day, high speed highways weren't as prevalent, so many of these old Fords were never run persistently on what we consider the highway, so it wasn't too much of an issue. Which leads to your needing to check the rear end ratio. There's a fair chance it's a 4.11, maybe a 3.78. Rare chance it's a 3.54. If you're ultra lucky you've got a Columbia two speed (overdrive rear axle). The normal gear ratios are intended for the predominant driving mode of the day; stop and go city or lower speed country driving. These engines don't like running 3000rpm or over for extended periods without sufficient modification.

Used as intended they can be a satisfactory power plant, but in modern terms that would be mild use. If it needs more work they can be an expensive rebuilt, $4-5000 is pretty common. With today's nostalgia craze there's a lot of interest in these engines, but don't let romance sway reality.