won't be backwards if it works as you say, and 10.5 or 11" doesn't really matter as long as you got the whole kit, they came with either originally, but there may still be a mis-match somewhere with an old 4 speed and aging clutch fork parts
a trans shop wouldn't be any different, they're heavy on automatics nowadays, not old school clutches, you maybe just need older mechanics with way-back experience .... I'd suspect defective Chinese parts [throwout] and/or possibly worn clutch fork, maybe slightly oversize pilot bushing allowing the input shaft to wobble .... I've had similar noises with new clutch parts - too bad you didn't just get a correct clutch kit from NAPA, they have a good warranty, just took the whole works back and got new .... of course you're stuck with paying someone to do the R&R
Bill
