Regarding the oil pressure question, I used a 96 Dakota harness merged with a 99 Ram engine harness and the 99 JTEC computer for 5.2L. The motor fired up without the oil pressure sender hooked up. I think its only there just to send on to the gages.
I am very interested in the Speedo question, we are using the 46RE and trying to use an aftermarket speedo.
