Having just picked up an M5A1/Recce kit, and planning on the latter, I think that an interior kit, along with a couple of standing crew seems to be a reasonable candidate for a resin add-on. I took a look at Pinky's old thread regarding his kit-bash & agree that it's quite hard to find images of the M5 version's interior (does the Hunicutt Stuart book have any useful images?) - though I realise that the conversions were on fairly ad-hoc basis.