Since the oil pump will make 45 psi, at least at start up, it might be ok.
I'm going to make an experienced guess and say the engine could be badly sludged up. Remove the valve cover and take a look, if you see anything that looks like what's in this engine
http://www.tegger.com/hondafaq/sludg...ng_sludge.html
then drop the oil pan (probably no need to remove the head like they do in the link) and clean all the sludge out, or as much as you can. A shop vac, solvent, a lot of rags and compressed air will be useful for this chore. Also dont forget the new gaskets.
After that test the oil pressure again. If its still low, the engine could just be, well, worn out...