Engine Rattling

[DoubleL]

Wonder if you guys have any input here. My truck has started rattling pretty bad. It is especially noticable under load. This is a rattle up higher not a low rod knock sound. It seems louder than a valve adjustment need. I am wondering about two things. I changed the oil a few months back and didn't notice if it had Zinc in it. I have just recently found out my 292 needs this for lubrication. I also have an old HEI distributor and I noticed it is a little rusty inside and I am suspicious of the timing being set right. I am going to get a zinc supplement and have already bought a new HEI unit to install. I recently rewired the truck and converted to gauges. I just got the part to connect my oil pressure gauge so I can check that out too. I guess i just want to know if I'm on the right track here and if there is anything else you all would check.