The big oil systems are split into 2 basic catagories; the twin OEM style, and the gear pump style.
The Terminator and the Stealth both use twin OEM PSD
style pumps inline using a special shaft and adaptor plate. OBS
trucks have to use a different fuel system as the fuel bowl is too tall with them.
BTS uses a mix of the two. Their pump is a OEM piston pump, but not from PSD
motors. They use a gear and run their pump off the OEM HPOP
gear. They use a SD
oil reservoir and a SD
fuel bowl. If you don't know what you're looking at, it really looks stock because the adaptor block is so small and covered up with other stuff.
The Gen3 uses a (I believe hydraulic) gear pump mounted on a IH T444E reservoir. It can use the stock OBS
fuel system, but it requires some creative mounting of the fuel canister. The Gen3 system utilizes a gear drive similar to the BTS system. There was an issue with a Gen3 hose causing a fire, but that has since been replaced with solid steel lines.
Some people have expressed opinions that the inline systems put too much stress on the first shaft, creating a possible breakage point. I have not seen any reports of this.
Others have stated that the gear lash on the gear drive systems needs to have a method to adjust lash. The BTS system has this. I personally don't think it is necessary with the Gen3 system because the manufacturing tolerances on the T444E reservoir are made to keep the gear lash within spec.
Dual IPRs is a constantly debated topic, with some saying that they're not necessary with programming. Others say that they are necessary to run in stock mode. As I understand it, the stalling problem is normally noticable on manual trans trucks. BTS, Terminator, and Gen3 use a single IPR
. Stealth normally comes with 1, and has instructions on how to add a 2nd.
There is/was a pump known as the Psychopump that replaced the OEM pump completely. It was a fairly large displacement gear pump, but it had warm start issues. These have apparently been resolved, but no more production has been announced.
Very good results have been seen from all the big oil systems. Cale Thompson (of BTS) runs their system on his twin turbo truck at about 700hp. It was also the choice (as if there was any other) for the white truck that Alan Black has. That system will be going on his wife's Expedition due to unforeseen circumstances. Elmo I believe runs the Terminator, along with almost everybody else on this site.
The inline OEM pumps are especially nice for most compound setups because that room is usually wasted (or not used well) otherwise. But, Cale's truck has compounds & their oil system. Someone else made a lookalike to a Gen3 system and had it running triples for a while.
All four are good systems. All four have had some growing/development pains. All four are making HPO for some strong running trucks. The choice is yours.