I realize this thread is about a year old, but I thought to add.
As a preventive measure, I decided to pull the radiator from my '68 Utility.
I (wrongly) assumed since it's a factory born 396 it was a 4 core since the truck is all original unmolested, yet it turns out it is in fact a 3 core.
First, the part# on the rubber mount(s) is 3889073 (as photos show).
I took some
measurements of the PADS, showing they are about 3/4" wide, by approximately 3 3/4" long.
This would indicate these are correct for a factory 3-core (or 2 core) radiator. Noting that on my radiator tanks, there physically is no room where these tanks could accommodate a 4-row core.
I'm including additional information below, but
I'm still wondering...any others out there with an original Big Block with a 3-core radiator?
Additional info on radiator pad fitment:
In a nutshell, from what I see, if the PADS measure around 3/4 " wide x 3 3/4" long, it's my belief they will only work for a 2 or 3 core radiator.
I believe the 4 core pads are about 1" wide and 4" long
With that said, I was talking with MrMudd (Greg) where on his truck ( a '72?) the radiator is a 3-core, yet the tanks are wide enough, where they could accommodate a 4-row core.
Many may already know this, and again, I'm simply adding information to a thread I found useful, but the tank measurement is important when considering fitment for a 3 or 4 core radiator with the respective pad mounts. In Greg's example his radiator is (technically speaking) a 3-core, YET his radiator must be mounted with the FOUR core mounts/pads since the TANK is wide enough where his core could actually be a 3 or 4 core.
Kevin