Water temp and oil pressure gauge no longer work with new engine

[Texarado]

I am in need of some electrical expertise. I just swapped out a good running 302 for a stroker 393. I am and have been using auto meter gauges
and they have always worked perfect until now. I installed all new sending units from Oreilleys in the new engine and yes i got the ones for the gauge and not the light. At first both gauges were pegging out as soon as you turn key on but now only the oil temp gauge pegs out and the water gauge goes to 180 and steadily climbs to 250. I have swapped out to manual gauges and i get good readings on water and oil pressure, although the oil pressure only reads about 10 to 15 psi when warm, but that is for another discussion. I have also swapped out to the sending units that were on the 302 and the same thing happens.
The motor is ground to the frame and to the chassis and the gauges are properly grounded and i get good voltage to the wires coming from the gauge. I am really at a lost because these are nice gauges and i don't want to switch to a manual gauge setup.
I hope i can get some help on this, i am about at my wits end!!

[Canonman67]

Do you have another electrical gauge to try? It sounds to me like the gauges have gone bad. If you tried the old sending units and get the same result it's probably a bad gauge, ground or maybe the signal wires were crushed when installing the new motor causing a short?

[HIO Silver]

Autometer's gauges are matched to specific senders... you cannot just use the stock, off the shelf senders.