Hi,
I am not sure about the drums, but a stock K&L wont fit a 70 bay as the beam bolt fixings are in a different place, unless it's a aftermarket beam, they sometime have both sets of holes i think.
Is it defo a 70? Check M codes/chassis number, if it's a 69 model year, IIRC they have the earlier bolt fixings on the chassis
Alistair