you mean ppm?
i think the Jeep is at 8000 pulses per mile output from VSS.
OK, that goes along with this;
The construction of the sensor was changed after 1992. Through 1992, the sensor has a glass enclosed reed switch: an eight pole magnet rotates which causes the reed switch ‘pulse’ once for each pass of a pole of the magnet. The speed/distance sensor is mounted on the transmission and the gear pinion gear rotates the magnet. One end of the reed contact is grounded and the other is connected to a 5v supplied by the ECU. The magnet closes the contact 8 times per turn of the revolution of the center shaft of the sensor. This means that it rotates 1000 times per mile or 8000 pulses per mile. Because the earlier style used a glass enclosed reed switch they are prone to failure.
In 1993 and later cars, the sensor uses solid state Hall Effect components to replace the contacts of the earlier style.
What about the newer Jeeps with the Hall sensor? Same? If I went with the mechanical speedo, I would just drop in my gear set and be done but that's too easy.
After just finishing the Dusy, I spent 99% of the time in the 4:1. I did use both boxes in low climbing Thompson Hill. But I could have done it without using both. It does come in handy.
I have been a strong supporter of the 4 speed type boxes for years. I still stand behind them. You might not need the 11:1 but it is nice to have choices depending on your trail. For me the 5.38's and the 4:1 are a pretty good combo and I don't use both boxes much since going to the 5.38's.
I would imagine the 4.3 2 speed would do just about everything you want to do. But think about how many times you use the stock 2.7 and would miss it. And think about the places you wish you had a 4:1. You could have both if you feel the need for both. IMO $800-1000 is not to bad to have such choices.
As for motor swaps think about the GM 4.3. Plenty of power, can be hooked to the auto of choice ( I would do a stick) it's shorter and can be moved forward to make up for DS length.
I'm sure I'd miss 2.72 on the rare occasion. Then again, I've always found 2.72 to be either not low enough or too high. I don't really hate 2.72 but I'm sure once I get rid of it, I'll miss it. It's how the world goes round.
For the power and simplicity, I'd rather do a 5.3L or a 6.2L. I've driven a 4.3L with a 4L60E extensively and it's ok. 8L60 is shorter then a 4L80, IIRC. A bare minimum would be a L05 5.7L. Phil Howell has me thinking of a 5.3L after doing one in their 2.5L.