Oil pressure gauge/oil filter

[Mertz]

The original engine in my truck didn’t have a oil filter and the new industrial engine now in the truck did. The filter uses the port in front of the distributor where the oil pressure gauge was plumbed. The filter line and the gauge line are different sizes. Can I put a tee in the line with a reducer and have the gauge still work?  If not how do I plumb the filter?  There’s a male fitting coming out the back of the block but I don’t know what it’s for. 

[Young Ed]

Usually the filter uses the 2 just behind the dist and the gauge uses one all the way at the back of the block towards the firewall 

[Mertz]

Great I can make that work.