I have seen a 454 in an '84 S-10. As mentioned the steering shaft was modified and the firewall was also cut to allow it to fit. I saw the truck just after the motor had been dropped in and the rest of the front end was off, so I can't give you much help with inner fender to motor or radiator to motor clearances. To give you some idea though, the top/front portion of the dizzy cap sat just a little aft of where a plumb bob would point to while attached to the bottom of the rear view mirror. I am not saying that this is an absolute necessity, just what I saw. This guy had drag racing in mind when building it, so that might have just been done for weight transfer.

You would also have to make some modifications to the motor mounts as well depending on your overall measurements. I would also suggest streangthening the suspension to accomodate the extra weight.

I haven't seen a kit to accomplish such a task, but then again I haven't been looking for one either.

Anyway, I hope this helps at least a little bit.

Cheers,
Firechicken