1750 gasser is fuel starved

Got my newest project up and running today. It was a 1750 diesel but the previous owner didn't think to put antifreeze in for the winter so the diesel was removed and we installed a gas engine that I got in a swap. So no history for me on this engine. Fixed a throttle problem where the linkage was installed wrong and it was hanging up on the engine block. Seemed to run really nice every time I got on it to use it a little. I did have fuel leaking out of the lower power adjusting needle. The o ring was slightly damaged and I couldn't find one to fit so I turned the o ring around and reinstalled. The leak stopped. I set the power adjusting as the book said to make sure it ran. Here's the problem, under load the tractor starves itself for fuel. At first i thought it was electrical but that was quickly ruled out. If i let it sit for 5 minutes, it would start right up at idle and act normal. At 1600 rpms, it ran good until it ran out of fuel. The tank was from the diesel and there is no strainer on it. I did install an inline filter. I also had to replace the pump because it was leaking fuel on the outside and into the crank case. So now I am stumped. Uses a Marvel Schebler USX-44. Haven't gotten the kit yet but was planning on it. Anything else I missed. The idle mixture may not have been set right, but after resetting it, i didn't get a chance to try it. I see there is a screen that I can remove. Probably try that next. Any other ideas would be appreciated.