The material that works for a flat-tappet valvetrain does not work for a roller-follower valvetrain. A billet steel camshaft is totally incompatible with flat tappets, it doesn't matter what the steel strength is, the cam tips will gall and fail within hours. Roller tappets require high-strength steel cam lobes. Production flat tappet engines use a process called "chilled iron" casting where the cast iron camshaft mold has "chills" as part of the mold to create a quick hardening of the cam lobes, which forms carbide at the surface of the cam lobes. Flame-hardened cast-iron is a low-cost and less-durable alternative. If the shop knows what they are doing and use the correct weld-metal, they might be able to create an acceptable surface for a flat tappet. When you re-grind a chilled-iron cam, the objective is to not totally remove the thin layer of carbide (especially on the lobe tip) so you still have carbide running on the steel tappet. I know the above from my experience as a valvetrain engineer.Delta said they could weld my 1ZZ cams back in 2014, and they still advertise welding on their website, so idk. The price was pretty reasonable when I asked back then, I think it was 275 for weld + grind on one camshaft.