RE: 90 SP
Hi Sledge
The RCV90SP (& RCV91-CD) are similar in power to conventional 90 4-strokes, which is similar in power to a 60 4-stroke.
For this reason either the 90SP or 91CD should be suitable for the bearcat you're building.
I hope this helps. In addition the 90SP would allow you to use scale 4-bladed props which would look fantastic, you would need to check that there would be enough clearance for a 15.5x12 prop though.
I hope this helps. If you have any more questions, please do not hestiate to contact me.
Best regards
Laurenne