I've had good luck with Duane Wells in Michigan. He advertises in the V-8 Times. Make sure you send him plates that are nice and straight. Reasonable prices and good turn around time.
Regarding normal on-the-road-use, the NY State DMV will not register a plate that has been repainted (maybe they think law enforcement can't see or feel the embossed numbers/letters ? ) .... have to bring in the plate with photo when registering it so they can inspect it.
Use of NYS historic plates on public roads here is limited to travelling to/from car shows/rallies, trips for repairs (I would include non-ethanol gas stations) etc .... i.e. not intended for regular driving.
Bought a '47 plate in good condition; just had to polish it up; only one per car that year. I think it's a commercial plate but DMV didn't notice. Aside from travelling to car shows, I make note of "repair" places in the general direction I want to head. My one old plate has not "delayed" my local travel but I haven't been outside the State yet.
You were very lucky or you live nearby to threaten him. I had him do a set of 1939 plates that were my dad's new about 15 years ago and the work was perfect and the price very fair but it took about a year.Back then they never wanted any type of payment until plates were to be sent out at works completion. I sent him my dad's original set of 1937 plates that are on my coupe 10 years ago and they wanted paid up front and it took 2-3 years of hassle and bs by his wife. Really was relieved to get my dads plates and they are very nice but I will never deal with his wife again and listen to her fairytale after another.
Every time I called they gave me a different story. They went from almost done and just needing buffed out to not in primer yet, yadda yadda. I would've had no problem if they would have been up front with me from the beginning. I got nothing but lip service until I told them to just send my plates back, done or not. Then it only took another month of promises that if I would just hang in there another week.