Parts came in.
Here is the gasket, Gates part # 33668. For a pre-94 cummins B series there is only one gasket. The one I took out had writing on it to help clarify its orientation.
On the left is the old thermostat. On the right is the new one, Gates part #33758. It's a 180F thermostat and research suggested that the OEM temp was both 180F and 190F. Figure I'd try the 180F and if too low I can always swap in a warmer one.
Old one on the left (I estimate it was 190F), new one on the right. Earlier 6bt owners complained about the coolant temperature fluctuation with the thermostat cycling open and closed. The eventual fix was to add more bypass holes (also called jiggle pins) to the thermostat. I never had temperature cycling issues on my 4bt and it looks like I had one of the updated thermostats installed. The new thermostat did not have the same number of bypass holes so I decided to add some myself; two 1/8" holes down at the bottom. The other reason I wanted to add some bypass ports is to allow some of the pressure to bleed out into the radiator before the thermostat opens. My theory is that this might reduce the possibility of building too much pressure to pop a freeze plug prior to a fully open thermostat.
The main reason for a jiggle pin is to allow the trapped air a way to exit for burping. It's recommended to install that port in the 12 o'clock position when installing the thermostat. This is my housing with that port in the 12 o'clock position. Spread some sealant on a few spots and put it back together.
Next, on to the freeze plug. It was machined out of aluminum and the bolt is stainless.
Applied some sealant around the o-ring and in the bolt pocket and tightened it down. I let the sealant cure over night before adding any coolant to the system.
I put everything back together and did some filling and burping. She started up and ran without issue. I let her warm up for a while to see if there were any leaks and so far all's well. I took it out yesterday and drove it today to work and I noticed it does take longer to warm up. Operating temperature is a needle width below my 190F mark on my manual gauge which is a little lower than before. I'd like to stay in the 190F to 205F range for operation so I'll probably need to adjust my fan controller to turn the fans on at a little higher temp. I'll run this for a week to see how it sits and to help expel any air still in the system.
Decided on an M&H inc. M3 fuel pin as it looks to have a little better fueling control at pre to low-boost than the Denny T stage 1 I had narrowed it down too. Gave them a call and they are out of stock until the middle of the month so I got put on the waiting list. That was fine by me. With all these fueling adjustments my TPS for my tranny controller is reading a little different and I'll want to adjust some shift parameters but I might just wait until the fuel pin comes. For now she drives civil cruising around at less than half throttle but above half throttle it's ridiculous that it is just a 4 cylinder diesel. Dora has become rather fun to drive.
5x.012 seems to be a better injector for this motor (at street power levels anyway) based on what I've read on 4BTSwaps, sounds like you're confirming that.
, but Dora didn't make it home on her own 
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