I've got a 76 300D- not very well maintained by it's previous owner, but I'm trying to make it functional.

Here's the sitch: Car was suffering from a huge loss of power, which I assumed to be fuel filters because I just started running it on B100. We changed all filters, fuel and air, adjusted the valves and ran diesel purge through it. Also changed a leaky fuel line at the tank. Started it up and it ran better, but still won't go over 30mph up even slight hills. Took a look and it appears to be drawing air into the fuel lines (inline filter won't fill up) and from testing it out, we determined that it's drawing in air before the inline filter. All lines before the filter appear to be solid and tightened and there are no fuel leaks under the car. What's going on??

Probably not relevant, but I'm told car has a vacuum diaphram leak, which is responsible for stiff breaks and smoking as well.

Thanks so much...this forum is keeping me sane.