Remember, even the Supras have issues. Nothing in this catagory is a have your cake and eat it too type of thing. I personally would go with a medium sized single turbo and a real good boost controller. The short block can be whatever you want 355 or 383 just use good components and have someone build it who has experience with building turbo short blocks. If you want to run big power on pump gas, turbo is the way to go if you are dead set on keeping it an LT1.

If not, get someone to build you a 10-1 427+ ci small block with 18*, 15* or SB2.2 heads and make it N/A. It should still be reliable assuming you use the right parts. The only issues will be changing valve springs and re-building lifters every x number of miles depending on how hard you drive it. This motor will however swallow every bit of that motor budget and perhaps a little more.