40 amps at stall is not that much compared to many of the alternative motors available or even a 12v gold which stalls at more than that. If geared correctly I doubt you would have any trouble with a 25 or 30 amp continous rated speedo.
Ian is right in most bots drive trains they will hot, very hot is pushed to hard.

As for needing sanyo C cells to run them this is rubbish, Thuggernought runs 2Ah sub C sanyos on a pair of golds at 24V and we have had no trouble with them and will easily run 2 fights without charging and they are only ever warm after a bout never hot.

The charger issue is a problem but can be over come with 2 18v packs or even 3 12v packs.

The golds in thuggernought are not worked to hard and we are thinking about 30/36v the main problems we have are - new batteries (want matching packs and need a different shape), More weight (We are a bit under but n ot enough) and the fact the electronise speedos are rated to only 24v and I personaly would not like to run them over 30v.