I'm really confused. Just because it came out of a truck doesn't mean it's a truck motor unless it came from the factory in the truck. If indeed it's a true truck motor it's a tall block, and the intake and some other parts also wont fit.
If I was you I'd post the numbers or check them yourself before making any decisions. Once you know what the motor really is, then you can decide if you'll use it or leave it for your dad. If it's not a truck motor I'd definitely go with the 427.

 

You're saying you have an LT1. Is it the generation II 1992-97 LT1, or generation I 1970-72 LT-1 (note the dash)? One is easier to swap in than the other.
Here's how to easily spot a truck BB:

 

Thanks for the tip 69. I did not know that.

 

That's a nice picture! Explains it better than words can!

 

I will be getting casting numbers today and having my dad take a look at it. Working in the oilfeild suck.........Im gone for 30 days at a time and have no way of looking at crap 1st hand. Are the casting #'s located on the bellhousing mount of a BB also? The Lt1 is 94 FI engine that has a carb GMPP intake on it. It came from a Buick Roadmaster, but has some interesting back ground. The heads are cast with the D-port exhaust, and insted of the dished pistons that the Baby Lt's got it has flat tops with 4 valve releifs in the top. The pistons are not aftermarket and GM cast into the underside. From research the motor is what some Gm employees called a BASTERD motor............It was a motor that Gm was experimenting with using diff combos of parts while in the development stages of the LS motor. Some where boat anchors while some showed massive gains.........so much as to be more powerful than the current Corvette. The project was suspended for some reason and all th motors weather good or bad found there way into production cars. The block is the only casting number that even maches anything for a B-Body. this motor was pulled from a running car at a local PIck&pull.....I wached them drive it in and it sounded like a stock car. I found a stack of receipts in the glove box from O'Relliey's for basicly everthing you could replace under the hood...........upon closer inspection I found that the waterpump drive had been sheared ( most likely from a bad water pump) and durring replacement the mechanic had no clue about what he was doing and didnot replace the drive shaft or coupling. So in the long run they couldnot find the overheating issue and the car made its way to the yard. Now Im not 110% sure of the truthfullness of the story I was fed about the motor........I do know I personally had the motor apart so I could check the bearings and replace the gaskets.......the motor looked like it was brand new, the bearings had absolutly no signs of wear, and well the pistons suprised the hell out of me because I was expecting dish tops. In the end every Cyl had between 220-240psi when dry checked with a compression gauge.

 

The info you need is on the front of the engine at the passenger side front. Look at the boss right above the water pump bolts on that side. It will give you everything needed.

 

Casting number reveiled its a 68-84 heavy duty truck block. The heads are oval port which is the truck heads. looks like Im going with the carbed Lt1 and prob the auto trans <-------still not sure about the tran as of yet. The auto would just be a direct replacement and the 4spd would need all of the parts from a doner car.