I am going ahead with an rebuild on my 312 original specs. Question, would it be wise to change the oil and water pump at the same time and brand Thanksif so what would be the best choice
This is hard to say without knowing the overall condition of the engine and components. I think NAPA and Carquest have listings for rebuilt waterpumps. The only choice for a new pump is Melling that I know of, rebuild kits are still available from the above stores. I think Mummert is gearing up to reproduce Frank Rice's alum water pumps, don't know if they are available yet.
I think a new oil pump during a rebuild is very necessary.
As a general rule on most engines, I would agree with you, but the Y block is a little different. There are two styles of oil pumps for the Y, the common gear type pump (still available from Melling) and the Gearator style (not available new any more). This pump was available in two styles, alum case and cast iron case. Many engine builders including Ted Eaton fill that this style pump has advantages over the gear style, and that the cast iron case is more stable than the alum case. Rebuild kits are still avalable for both styles of pumps. If the case is not worn and still in spec, no reason not to put a kit in and reuse it.