Boring an engine is part of a rebuild, you have to pull the engine and completely disassemble it once bored you would need new pistons and rings, resized rods, rebalance the rotating assembly. as I stated I would not waste time doing this to a 305, the cost for machining, assembly and parts are going to be the same price for a 350 as a 305.
As far as Rhoads lifters they were designed to help with bigger cams making them more "streetable" and are not going to solve any flat tappet wear issues.
If your lifters were worn badly then all of those metal shavings are throughout the engine so it would just be a matter of time before the damage from that happens.