oic. I've never seen one of those pumps myself. 20 gallons per minute wouldn't be enough for me so I never gave them a second thought. I'd ask www.dedenbear.com directly.
Sounds like a tight squeeze to me. My truck is kinda tight too, so I know what you're going thru. I moved my radiator forward as far as I could.
Post some pix when you get that motor in there. I have an '85 190E that is in good shape except the motor is tired. I think a chevy V8 would be sweet in there too.