Yes, you can carefully bore out a smaller adaptor to accept a larger case. Just be sure you make it big enough to allow a belled case to come out. Don’t ask me how I know this!
Actually, the 45-70 case is large enough in diameter that one can just leave the adaptor out entirely. The process will go on fine without it, since the case comes close to filling the un-adapted hole in the tong tool. I have done this myself to run a few cases.
Froggie