350 throttle body conversion help

i recently just baught a 1988 350 throttle body and i converted it over to a pump gas im having problems with fuel pumps ive put 3 on it and none of them worked but i also put the chrome shaft to the cam in it and its out of a 305 i was just wondering if its to short? could someone help please ive been trying to pin point my problem for a week now and i cant figure it out my other alternative is to go to a 7-15 pound fuel pump that gets mounted on the fenderwall but any help or advice would be greatly appreaciated

Has the block-mounted fuel pump ever worked? If not, you may have a later SBC (roller cam). Most of these engines had camshafts with NO fuel pump lobe cast onto the billet.

http://72.19.213.157/files/LT1Camshafts.jpg

Notice that the upper (factory) camshaft has no pump lobe.