Sometimes it takes a few hundred, to a few thousand miles for the cleaners to work their magic. But if the lifters are not making noise then they're likely not sticking. I guess they could stick in a pumped-up position, not letting the valves close, but I think that would be unusual.
Have you given it a tune-up lately? What about a compression check?
Does it smoke or use oil?
When mine would run on 7 cylinders it was hardly noticeable other than a rough idle. When it ran on 6 though, it was pretty rough.
Could be so many things at this point.
The inter-compatibility is extensive. Mostly you just need to watch out for, and avoid completely the oddball V8's that were around sometime in the late seventies or early eighties I think, that were smaller than a 302 and had different components. (others here will know the details)
Otherwise you can use a 302 from '69 to '01 and have good luck doing all that.
The advantage to the '97 to '01 models is that they came in Explorers only, and had that great front accessory serpentine drive that everybody is scouring the junkyards for. The later blocks after a certain year ('89 or '91 maybe?) were roller cam equipped and had the more desirable "E7..." heads. The most desirable of all are the GT40 and GT40P heads from the Explorers.
The GT40P's were the pinnacle, but with their slightly odd spark plug angle are not considered to be quite as desirable for Bronco owners with headers not specifically clearanced for the P head plugs. But will accept carb intake manifolds I'm pretty sure.
There are certainly minor variations over the years, but I'm pretty sure there were only a very few that get in the way of you using a carburetor.
One consistent stumbling block though, is if you want to retain your mechanical fuel pump and if you have a manual trans.
The fuel pumps all went electric after a certain year and the front cover had no more place for a pump to mount. But if that's important then your old stuff will bolt right to the front. Even though they had like 30 different designs at one point, they ALL still bolt to the front of the engine block.
The later blocks were missing the one hole for the clutch linkage Z-bar setup. But that's easily overcome so most of us don't consider that an issue.
Good luck. Lots of good info around here. Lots of the members have detailed knowledge of doing just what you're doing.
Paul