66 C10 250 Fuel pump issue

[Sundy]

Hello all, I'm new, first post.

I either have a bad part out of the box or a real problem.

I bought a 66C10 with a 6 cylinder 250. When I got it it ran fine sitting still. When driving I get to 3rd gear it dies and takes a long time to restart, then it will run fine again.

The person I bought it from hand an electric fuel pump installed, which I didn't like the sound of anyway, so I installed a mechanical fuel pump. (Also replaced a nasty looking fuel sending unit) The new pump did nothing and it installed way too easily I think. I expected some resistance on the pump lever. After getting zero puming from this thing I took it off, cranked the engine until the cam offset was all the way facing the pump and put the pump back on. The lever doesn't even touch the cam as far as I can tell. There should be some resistance, right?

So, did I get the wrong fuel pump? It looks like the right thing but I didn't have one on there before so there's nothing to compare it to. Also, I can't move the lever by hand at all. Should it be all that stiff?

Or maybe this engine isn't what I was told and I've ordered the wrong fuel pump. But do they even vary from one to another on a chevy inline 6 cylinder?

Thanks in advance for any advice!
Sundy