electric fuel pump

[CJJ67]

I have a 67 stepside with a 350 sbc motor. I moved the gas tank from the cab and replaced it with the suburban tank on the rear frame this weekend. My problem is that the carb doesn't seem to get enough gas on start up. There is no gas in the filter, but as you keep turning over the motor, it eventually starts and runs fine. No stalls when driving or accelerating. If you let it sit for a while, the problem is there again. I hooked the lines on the tank up as: filler line and vent line is good, but the two remaing vent lines I installed a vent plug/valve like you would use on a motorcycle. What I was thinking was that maybe the gas lines that I used are too big for the mechanical fuel pump. I had some clean 3/8 in. stainless steel tubing left over and I used that. If this is the problem, would an electric fuel pump help or do I need to use smaller fuel line. Oh yeah, I've already used compressed air to blow out the lines and I installed the tank over two years ago, just never got around to hooking it up.

Thanks for the help