Well, the answers to my questions may be here but I have searched for a couple hours with no luck. I purchased a Hayes manual and it could not help me. I just purchased an 86 IROC w/ 305 carb engine. I am dropping in a 383 carb engine. I am removing all smog equipment. I want to use the original gauges. The 305 had an oil pressure sending unit on back of intake that I swapped over, the 305 was partially taken apart and the only thing missing is the t-stat housing and I assume that the water temp sending unit was in that(correct me if I am wrong), The knock sensor on the bottom of the block was tossed, there are two water temp type sending units, one in each head, not sure what they are for. What I am looking for is the wire colors for the tach, water temp gauge, oil press. gauge, volt meter and maybe a key switched hot wire in that harness for the HEI. One a side note, my block has a driver side dip stick and I did read that this may be a header fitment problem. I assume I will need to use shorty headers due to it having a T5 and the clutch slave cylinder being in the way. Any advice on that would be welcomed. Thanks in advance for any help.

I don't know wheather long tubes pose a fitment problem with the clutch slave or not. The comment I wanted to make is that getting rid of the slave and replacing it with Howe's hydraulic throw out bearing "for T5 with stock clutch" (pn 82876) and an adjustable master cylinder (either from Ram clutches or Mcleod) is one of the best upgrades I've done. You'd could then route the hydraulic hoses in whatever way is most convenient.
Just a thought.
Jon

Not sure if it's the same between my 1992 305 and a 1986 305 - but...

Pass block between 6 & 8 plugs = knock sensor - no longer needed for you
Pass head between 6 & 8 plug = fan switch - I hated those things and ditched it foe a seperate fan controller
Driver block between 1 & 3 plug = coolant sensor for guage

If I remember right - white wire for tach, pink wire for dizzy

Hope any of that helps!

I am sure it will get me heading in the right direction. Thanks

You won't need the sensors in the thermostat housing.