Its not really the shop you use, but the guy doing the work, everyone has bad day at work and in the machining business a bad day for the operator can be a heart stopper for the customer. Like has already been stated whenever you have any kind of work done you should check it all over thoroughly to make sure its dead on right. every motor problem I've ever had has been from an assembly problem not fualty machine work if you measure out a clearance and it isn't right or your not happy with it call the shop and have um fix it. for mustang stuff I would recomend Fox Lake I went up there with fowler to pick up some stuff and that place is so clean inside you could eat off the floor thats the kind of machine shop I like to use. Earick Racing is also the same way (newark oh) all sunnen equipment and very clean inside. I would get ahold of napa you shouldn't have a problem with them making it right if its their fualt. I've only dealt with the shop on the east side , but they always took care of any problem or concern I had without incident.
good luck