1983 C-30 Gage problems

[rrspeed]

I recently replaced my blown 6.2 diesel with a .030 over 454 in me restored 1983 C-30 crew cab dually I use to tow my car trailer. To make a long story short, the dash gages were working fine after the swap. I have a volt meter, oil pressure and water temp gage as well as mechanical gages. I had to replace the hydro boost unit and after I did, I noticed the oil pressure and water tempature gages weren't working. The oil pressure gages read at the max. (80) and the water temperature gage doesn't move at all. I already checked the wires going to the senders and they are ok. The senders check out as well. The only other thing I did was disconnect tyhe power amp and radio. I'm wondering if the ground for the radio might also be a common ground for the oil pressure and water temp. gages. Any suggestions would be greatly welcomed. I tried another set of factory gages we had from a truck that we were scrapping and they did the same thing. I'm using a Summit street/strip ignition box, distributor and amplifier. The ignition requires a diode to be used in the alternator wiring to prevent run-on. I'm wondering if that might be affecting the gages as well. It just seems old that only the oil and water temp gages are affected and not the voltmeter.