3 litre ford help

from previous threads you will see that early last year i pulled the 3 l from a 94 ranger and put in new rod and main bearings and a new oil pump and that the engine had no sludge at all when taken apart and that oil pressure was ai 50 hot ar1500 rpm and 20 at idle and that ithought the idle pressure a bit low.. ran fine since then but about 2 weeks ago developed a really loud lifter , was running like garbage and really lacking in power i have been working on it for the last day or so trying to figure out what happened before i take it apart. what i find so far is 1/ oil pressure at 20at 1500 rpm and 10 idle and is slow3 to develop from cold start 2/vacumn reading on the low side 3/ timing and advance bang on 4/very low on power 5/ runs like garbage but actually other than the loud lifter idles pretty good 6 / no oil contamination 7/ compression in the 150 range 8/ no over heating from the catalytic or rotten egg smell i am really concerned as to the oil pressure as i am sure its all tied in together and the last thing i wanted to do was pull it out again one one thread i red that this engine had camshaft bearings that could give trouble help sam

pulled the intake off and found one lifter screwed but also found what was left of a cam bearing laying beside one of the lobes. ibefore i pulled it apart i replaced the oil filter with one from ford . and this brought the pressure back to 40 at 1500rpm and 18 at idle even with the cam bearing gone,. but in any case the engine has to come out and i will decide on path of action from there i.e rebuild, get a used one or buy a new one sam

found a good used one but the donor is a 93 ranger with a standard tranny while mine is a 93 with an automatic. what problems can i expect to run into thanks sam

also foud a really good 4l but i have no idea as to its compatability but if easy i would consider