I just recently finished a 351w swap in my 96 F150. It runs good but uses oil and smokes when you give it more than half throttle and really bad under full throttle. I thought it was a pcv problem but I fixed them for the most part. It is a stock short block out of a 96 F150 with 116k. It was clean inside, the miles were reasonably low and it didn't smoke in the truck I pulled it from so I deemed a rebuild not necessary. The 302 I replaced had 355k and I never had to add oil between changes. Last night I did a compression check:
1 - 175
2 - 135
3 - 175
4 - 155
5 - 185
6 - 190
7 - 165
8 - 125

What are some possible problems I could be facing? I thought it was bad valve seals but now I see the compression on cyl 2 and 8 are quite low. I did not perform a leak down yet but I will soon.

 

Could be bad rings.. That would lower the compression and also allow oil to pass through. I am not sure what the tolerance is supposed to be cause you also have between 155 and 190... That might be worth looking into also.