You shouldn't be having problems with the A. If my old worn out L18 could haul a 620 up all kinds of hills, the A should haul your lighter car up hills. It's like a Honda (kill me now) and needs to be revved higher like ggzilla stated. If it can't handle being revved, the engine is not in good shape and there are other problems. You should never try to pull hills in 5th gear, especially with lower HP engines.
If you are serious about doing a swap, I believe the A10 cross member is a direct swap and has better mounting points for the KA. A single cam KA should be easy to find and you can grab a CAN/AM box from steroid on here (if they still make them) to make wiring easy. However you will need to upgrade your rear end to handle the torque since you are young and basicly stated that you will be running it hard. get the cost of everything you need (engine, trans, cross member, can/am, ecu, maf, mounts, radiator, fan setup, exhaust work, trans cross member, and possibly a 510 station wagon rear end) multiply the cost by 2 and that is what you are probably looking at cost wise.