4.6 serpentine no oil pressure after pump change

I'm having problems with my RRC softdash 4.6 conversion.
I had it running but it was taking time fro the oil pressure light to do out, on investigating found that the oil pump was worn (it was the original from the RRCs 3.9). So a much less worn pump was sourced.
While I fitted this I also changed the oil pickup pipe in the sump as I knew this had been bent in the past, and on comparison with the replacement did indeed find the original out of shape.
I tried cranking the engine over today to build up oil pressure and the light stayed on so it looks like no oil pressure. I know V8s of old you had to pack the external pump with Vaseline or similar and then spin them with a drill from the distributor hole, but no mention of this need for the crank driven oil pump on the later engines, is there any way to prime them or has something gone horribly wrong?

since the pumps above oil level i do allways pack pump with vaseline as a primer

As it all back together now, would it be beneficial taking the oil cooler pipe off the top of the radiator and syringing oil down that? The filter was filled with oil. Whats odd is I had the old oil pump off a few times and that seemed to prime OK despite having gears that looked like they had been sand blasted and side with a lot of scoreing!