A product I have used for years to remove lettering is ELO (Easy Lift Off). Paint it on over the lettering and let it soak for a few minutes, then remove. Repeat, after a couple applications the lettering will come off using a paint brush. When done make sure you wash the part in warm water to neutralize ELO, if you don't it will keep on working. You only have to buy this once, I bought a pint bottle more than two decades ago and it still looks full.