Oh, my, god. The SOHC 3.0L 3vz-e V6 in the 87-94 truck platform is the worst "modern" engine Toyota has ever put together. It has no redeeming quality.
NOT to be confused with the 3.0L DOHC 3vz-fe found in the cars.
The other '87 v6 that's just 2.5L and DOHC from the cars (2vz-fe) makes practically the same power. It's that bad!?!?!?!?
The head-gaskets are the good 'ole post first generation asbestos ban. They're easy to roast IF you overheat the engine, and they will blow almost every single time too. The great news, is that because it's roughly a 300lb bottom end, and how the coolant system routes... Basically you don't know you're overheating until it's too late. The shear amount of mass on the bottom end will let the coolant boil, then cool back down before it exits the block & get's to the post- engine coolant temp sensor.
To contribute to that, they use the worst header / crossover design... Ever... It doesn't just kill off around 20-25bhp (Which is SUBSTANTUAL on a bearly 150bhp engine), but it's so restrictive it causes massive amounts of heat in the #6 cylinder because it can't scavange the exhaust quickly enoguh.
This leads to superheating of the #6 exhaust valve, and not only do you destroy the valve, the head gasket blows betwene the #5 & #6 cylinders fairly predictably.
Now on the other hand... The 3.4L 5vz-fe is a great engine. It's a Toyota truck engine. Which means that it has massive torque on the low - mid range powerband, but it also has a relatively low redline & fuel cutoff (5200-5800rpm).
They're very good with boost. Provided you put a Multi-Layer-Steel headgasket on them for safety if you're really going at it. Otherwise you want to stick to sub 14psi. That way you keep the *peak* effective comression ratio under 13:1. Which is what I have accepted as good for the old gaskets.
The 5vz-fe is a great bottom end. It's your typical vastly overbuilt old school Toyota v6. Stock engines have been hitting 500-550bhp for years.
There are only a few 1uz-fe truck platform swaps that have floated around. Namely because most people with a 22r, 22r-te, or 3vz-e either do a 5vz-fe, or a 7m-gte swap.
They you've also got people that have been doing the 4.0L 1gr-fe, and 2uz-fe swaps more rescently
Of the lot I'd take a 5vz-fe, or a 1gr-fe. Prefferably with a single turbo on the way into the truck.