Here's what I have. A 72 Ford Bronco with a 302 with a OHG450 mixer on top of a 4 barrel throttle plate. This is being feed by a Model E regulator (just rebuilt) through an electric lock off. I can't get it to even ack like it wants to fire. I have spark at the plugs and propane to the mixer, but still no fire? Tank is full of propane and am using the manifold for my vacuum source. Still nothing?? Any suggestions or ideas??