I've always used some sort of exhaust pipe rubber hanger to mount electric pumps. It isolates the noise from the car pretty well. I did a search for a pic, but couldn't come up with the ones I used to buy (Pep Boys). Here's an example of what I'm talking about.....
http://www.automedia.com/Exhaust_Han...es20020401eh/1
These are not exactly the ones I've used, but should be better than solid mounting or rubber pads between the pump and mount point.

The other thing is, it sounds like you have the lines routed deadhead. The pump may run cooler and quieter if you run a return line with a regulator to set pressure at the carb inlet to around 5 1/2 lbs.

Here's a cute little exhaust insulator I found at Jegs that might work well and look sanitary also......
http://www.jegs.com/webapp/wcs/store...-1&showValue=1