Chaz;
I'm sorry to say, it sounds like you've been bitten by the HEAD GASKET BUG. In your mechanic's defense, he probably knew nothing about it, as only those familiar with these engines know the truth - and, here it is:
Ford used steel head gaskets on these engines that were .020" thick when assembled. ALL aftermarket head gaskets are either .045" thick (Victor/NAPA) or .055" thick (FelPro). So, if you had your head milled .010" and then used a Victor/NAPA gasket (which most auto shops do), then your compression went DOWN instead of UP. In addition, the pushrods are now SHORTER than they were before, which makes them all loose and rattly-sounding. I know this because it happened to me 2 years ago. You actually lose valve lift and power.
To be specific, if you milled .010" and used a Victor gasket, you lowered your compression from the original 9.0:1 to about 8.1:1 and your pushrods are now (.045"-.020")= .025" shorter than normal. If you used a FelPro gasket, you lowered compression to 7.8:1 and shortened the pushrods by (.055"-.020")= .035". Either way, you lost cam lift, at least .020" or so.
TO FIX THIS - get a thinner head gasket. The best approach is to get a steel FORD gasket from Mustangaroo IF YOU'RE GOOD AND FAST at putting it together, because you MUST USE SEALANT on the steel gaskets or else you'll spring oil and water leaks. The next best choice is to get one of Ford's genuine replacement composite gaskets (I have 2 left for sale) that are a conventional design, but are .007" thicker than the steel ones. The big difference is: these units are for the inexperienced mechanic because they are forgiving and seal better than the steel ones.
The steel ones from Mustangaroo will restore the compression you wanted 100%. So, if you milled, say .020" from the head, you'd get about 9.9:1 or so. With my gaskets you will get about 9.6:1 or so for the same mill amount, but easier installation and better sealing.
If you go with the steel, get 2 cans of the liquid Copper Permatex. As fast as you can, paint the bottom side, place the gasket on the block (use 2 head bolts to hold it in place), then quickly paint the upper side and assemble the head. If you take more than 20 minutes total to do this, it's too long.
One other thing: when you have the head off, look at the sharp ridge along the "flat" side of the combustion chamber. Take some emery cloth and smooth this down - you don't want it sharp or it will induce knock. Also, if you had a valve job done, you'll see the same sharp edge around the rim of the valves, each one. Although it's hard to do, remove the valves and sand down this ridge on every valve, ESPECIALLY the exhaust side (the smaller valves). This ridge can cut your flow down as much as 15%.
One last thing: if you did not replace the lifters, do it when you have the head off. New lifters add up to .015" lift over old ones, plus the milled head will raise the lift by approximately 20% of the mill height at mid-to-high engine speeds (that's like .005" extra for a .020" mill job).
Hope this helps: sorry for the bad news part, though.