adam - some thoughts -
alot, of course, depends on your intentions of use, but at a starting point - even though you already have some pre-amps you like, I would suggest that an older tascam mixer like the 308/ 312/ 320 would be a perfect match for that 38 R-R deck.
while these have pre-amps in every channel, they also have multiple inputs into every channel, mic in's which feeds to the internal preamp, and also have line in's, so you could use the external pre-amps where you want.
this older familiy of tascam mixers is only of a 4-buss design, but has direct outs and have tape return in as well, so even the 8 channel 308 mixer mates very nicely with a 8 track 38 deck.
these are often available fairly reasonably priced on ebay as well.
good luck
b-h