97 pont. transport upper engin knock/tick

I have a 97 Pont. transport with a 3.4L auto trans. It is making a real hard tick from the top half of the engine. Like some of the lifters are stuck or not getting pressure. I replaced all of the lifters so i know they are good but im not sure they are getting oil pressure. the oil light has not came on and there is not a guage on the dash . there doesn’t seem to be any oil moving/sloshing around in the valve covers when i look thru the oil fill cap either. Im fairly certain the pump is good because the lower half (crank,rods,mains)seems to be getting lube and pressure although im not sure how much. is there a way/place to connect an oil pressure gauge to check the oil pressure? and is there a common problem that this particular engine has with oil pressure/lifters?

OK. after reading a few other posts I realized I neglected to supply some important info. The van has 78K Mi. I bought it used, It has a lack of power, idles smooth,misses on acceleration,has all maintainance records up to date, ticking is extremely loud defiantly coming from top half of engine and does not go away after warm-up.