That pump may need a regulator. If you do not want to use a regulator, try the Carter Super Mechanical M6902. I just put one on my 340 a few weeks ago and it puts out 7psi and no need for a regulator with my carb.
http://chucker54.stores.yahoo.net/cam6sumefupu.html


1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)