Jamo,
We had a set of aluminum 351W heads come in, fresh out of the boxes from the manufacturer (when I was still at the speed shop) that were not even close to production dates from one to the other. The castings were so far off, that we spent several hours getting the two to flow the same...........People think that just because these items are brand new, that they do not need to be worked over by a professional to get them "just right"...Same goes for valve pocket porting, swirling, etc. This does not even touch on the basics of building a reliable lower end of a motor, just an overbore does not do it. Cleaning it out, line boring, honing, matching piston rings, chamfering, stress relieving, opening up the
oil passages, etc and so forth.. Damn, I can go on and on with this, and I'm not even a trained mechanic (nor do I play one on television) or engine builder, yet I still know the importance of doing it right the first time. The last thing you want to do is have to pull the engine out of the car once it's installed because you decided to cut corners and take chances with fitment or parts matching..................Especially with a FE motor...................Even small mistakes can be costly ones..............................
Yours In Fords,
Bill S.