Regarding fears that the LT1 has too much top end and not enough torque, and is only suitable for a "gallon of milk", you have to look at the original stovebolt engines in these trucks. I had a 235 in my 52 3/4 ton that probably only had around 200 lb-ft and barely over 100 hp, and I've loaded that truck with amazing amounts of cargo and even towed with it for 400 mile distances.
Compared with the straight six engines, the LT1 is a powerhouse and would be more than adequate.
Regarding the LS1 engine, I would personally try to get ahold of a 6 speed manual F-body transmission with that double overdrive. With the extremely tall overdrive options, you could keep your short rear end gears in the truck and not have to worry about it.
Go to Speedway Motors to get a traditional V8 engine mount kit adapter for the LS1 engine. Then adapting your 283 to an LS1 is a no-brainer.
And yes, the LS1 has big-block like torque, but there are still big blocks with far greater torque. The BOP 455, for example, have nearly 600 lb-ft of torque with mild mods that will still run on pump gas. The 454 and 427 have over 500 lb-ft of torque on pump gas (more when built up). The LS1 does compare with some big blocks, but doesn't have more torque than all big blocks.
It is, however, a great choice that will give you big-block like power with the economy of many 4-bangers.
Good choice.
Question...how is your steering box set up for the V8?
