GM 6.6 (L8T) repower good hp and torque using 87 octane fuel a good option especially if you have a high mileage engine a slight bump up in fuel economy. Another option and IMHO the ultimate H2 upgrade a GM Duramax/Allison combo, 25mpg economy and torque that just cant be beat.

OR, forget buying an H2 and save yourself lots of work and go buy a new Hummer EV. (don't forget to start saving for the estimated 25-35k battery replacement costs.)

As many have said, if it ain't broke don't fix it, lol

 

I have the Predator Hummer with Duramax upgrade. The magic of the Duramax upgrade is that all OEM buttons and features work. Predator took the time to remap everything and test it out. If you love your Hummer and want more power, it is the safe, proven way to go. It is not cheap and will cost between $35-40k.

* More power when you need it
* Slightly better fuel economy... I say slightly because with the new power, your foot gets heavy and you lose a lot of the fuel economy benefits :-)
* Driver controls are all OEM
* Sounds amazing
* If you want to go offroading, camping, or overlanding this is your best option as you just can't do that in an EV

If you love your Hummer and you want to breath new life into it... this is it.

 

For those stuck on batteries, here is the real future of the electric car: