I know nearly everyone here hates the 3VZ and loves the 5VZ (3.0 and 3.4 respectively), but when you look at the math, they aren't actually all that different.

150HP/3.0L = 50HP/L
180lb-ft/3.0L = 60lb-ft/L

190HP/3.4L = 55HP/L
220lb-ft/3.4L = 64.7lb-ft/L

The 3.4 isn't actually that much better, displacement-to-power wise. Yes, I have driven both, and yes, I acknowledge that it is a night and day difference. I'm simply talking math here.

Here's where my crazy idea comes out, feel free to laugh at me.

Hypothetical situation (truly): someone with a 3VZ-E powered Truck or 4Runner has the bottom end go out. They don't want to go through the trouble of a full 3.4 swap. Would the 3VZ heads bolt to the 5VZ block? Essentially, you'd wind up with a 5VZ-E. Especially if you are living in California, this would greatly simplify smog checks, since all the original intake/heads/emissions stuff would bolt on (maybe?). I don't kid myself that you'd get as many gains as a DOHC 3.4, but an SOHC 3.4 should yield some nice results, I'd think.

I know this isn't the case, but assuming the HP/L numbers stayed the same, you'd wind up with 170HP and 204lb-ft.

Something to think about anyway.