If the 'ridge' is the machined ridge that is used by the valve spring retainers, I'd vote for removing the head. And doing a thorough inspection of all valves and the other head.
When you have the rocker arms and shaft off, all the valve stems should be at the same height.
I did have a 302 once that had multiple diameter valve stems on the same head. From the factory. Must have been a 'broken tool' head that was salvaged by oversizing one valve guide. I had to search all over for an oversize stem replacement.
Glad you got it, I went threw the the same issues in my 340, between the guides being too long for my cam lift, bending push rods and whipping out cam lobes, I hope my issues are resolved. If they disassemble your heads and go over them, let them know what cam your running to make sure you have enough spring pressure and clearance. Shops do make mistakes, a well know shop in my area put a guide in crooked on my dad's 352 PI heads, after he broke two rocker shafts, he installed girdles, 15 years later, had the heads redone and found the crooked guide, we still do business with them because they stand behind and still do good work. I'm gonna go see my dad's 410 in his highboy, it should be a screamer! (That's why I need my scj 460 done!) Good Luck and keep us posted!
I know this post was last written to 4 years ago, but just in case someone does what I did and found this post looking for a lifter rattle or lifter tap noise, I wanted to post this. I was freaking out that I had a major engine problem. Had a really good engine builder tell me the noise was from exhaust gas leaking through the guides, or a collapsed lifter. I read some other posts that suggested it may be a fuel pump noise, but I blew off the advise thinking that the noise was too loud and too much like a lifter tap (or even a rod knock) to be a fuel pump noise. Guess what...it was the fuel pump. The noise went away just like a lifter that gets pumped up at higher engine speeds and oil pressure. I was never so happy to be wrong! Fuel pump noise it is!