If the 'pan' you are talking about goes between the fenders, behind the grill and at the bottom of the radiator, it is the 'radiator pan' or 'radiator valance' or 'radiator pan valance' or 'lower radiator shroud'. I think 'radiator pan' is the most common name.

With the grill off you can see that one of its purposes is to funnel the air into the radiator as well as keep the lower part of the front fenders together.

There is a thread on where to find one here somewhere. Try searcing 'radiator pan' or 'radiator valance.'

Someone put '54 fenders and grill on my '51 pick-up and I wanted to put it back to stock so I had to find that same piece. I've noticed a few on e-bay from time to time. They are out there, but only used or NOS, no re-pop.

I suggest posting in the 'parts wanted' forum.

'51 Chevy 1/2 ton w/'62 261, HEI, offy, fentons, dual carter/webbers, t-5 & 12 bolt posi