Tony,
I tried to reply before, but, for some reason, this forum now crashes my phone every time i try to reply...
Anyhow,
Jules had some issue with the gear pump on his burner, trying to run split FFAs. I cant recall the exact detals, but it was along the lines of HMPEs (or their equivalents) blocking the internal gauze on the pump, and then the seals breaking under suction - or somthing like that anyhow.
So, the gear pump may not do you for that long when trying to pump more viscous stuff. It may be fine for years, but jules's just didnt seem to last that long.
And, as above, i can confirm that they are driven by the same motor that does the fan. Its not variable speed, so you should be able to work out the rpm easy enough (i dont know how many pole, but it must be written somwhere)