Hard start...

So my 73 318 la 5.2 duster is hard to start. I just upgraded to a hei progressive ignition distributor. It has spark now but I literally have to hold in on start, like keep it on the starter and pump it with gas to get it to turn over. I know this is not sustainable as I will burn out the starter. Any thoughts or advice would be much appreciated.
Thanks
Gus and his green bastard ;)