When I bought our pump for diesel about 5 yrs ago, the Pacer mfg recommended "Buna-n" seal material. They had it in a separate package, post-installed by us. It works fine. Absolutely no comparison to 12V pumps in speed. We have 35' of 1" hose w/auto-shutoff nozzle on a portable tank.

I think I notice @ the farm shows recently, that there are an ever-increasing number of portable (on wheels) tank mfg. Now Alum-Line is in it with an all-aluminum chassis. Tank has to be steel they say due to regulations. But, it's $20K+ for 750 gal.

Seems that "buna-n" is same as nitrile rubber:

http://en.wikipedia.org/wiki/Nitrile_rubber

Here's the Pacer pump we have:

http://pacerpumps.com/files/econoAg_pb.pdf

Note that is says NOT TO PUMP GASOLINE!