Chevy small block question

I've got a early 80's car with a chevy 350 in it.
I was wondering if a newer (2002 or up) 5.3 liter will fit in place of the 350.
Are the measurements of the block close? I have heard thet the newer motors are wider and I might have a problem fitting the new motor between the frame rails. Any input would be appreciated.

It can be done, but the mounts are not the same and you will also need to supply all of the PCM wiring as well as a PCM itself. Transmission too. Probably too much hassle for this car - unless the car is super special to you and you want this newer engine in it, it's probably better to stick with the conventional SB.

I'll try to make this short and not bore you...
The car is a 1981 Checker Cab. It originally came with an Olds 350 diesel from the factory. Somewhere along the lines the motor was pulled out and someone started to install a Pontiac V-8 of some sort. These cars came with all GM drivetrains and you could select between a V6, V8, (305, or 350), or the diesel mentioned above. The motor was never fully installed anyway, so I thought I would really update it and make it more reliable and driveable. I can get the 5.3, trans, PCM, and harness - IT'S NOT CHEAP, but I think it would be sweet! I don't plan to do it all at once, due to time and costs, but wanted to know if a 2002ish 5.3 would fit. By the way - all engine choices came standard with a T400 transmission. I've got another Checker - 1977, 350 4bbl from the factory - runs and drives. Thanks, Bill

I'm actually familiar with the Checker Marathon, and I've seen the V6 and V8 versions. I know they all had a TH400 trans as well, and I think your mod, if fully performed, would make it sweet. There's not too many of those around any more and to see one modded like this would be sweet.

So, You think that with some custom mounts, I could fit the 5.3 and its trans into the car? The donor is a Chevy truck 2WD. I know all the cooling will need to be upgraded as well, but I had thoughts of dual electric fans behind a new 3 row (at least) radiator.
Thanks

So, You think that with some custom mounts, I could fit the 5.3 and its trans into the car? The donor is a Chevy truck 2WD. I know all the cooling will need to be upgraded as well, but I had thoughts of dual electric fans behind a new 3 row (at least) radiator.
Thanks

I know of a guy who took out his tired 3.8 liter and replaced it with a reman 4.3 from an early 90's GM truck. He kept the 400 trans - it is really very nice. It was basically a direct replacement except for the electronics, but he made that look easy too.