My car is a '64 544, and originally had the B18. Sometime in the past, it must have been in a crash, and was repaired with a B16 nose, all long before I ever got it. So I never had to really change anything at all to remove the original B18 and install the hopped up B20. The only weird thing on my car was the tube added to the bottom radiator fitting that reaches over to the other side to the B18/B20 water pump, that was done in the past when whomever it was put the B16 nose on the B18 car.

My point on the grilles is that the decorative grille surrounds will fit on either style nose section, if you wanted to put a b18 nose on the car, you could still keep your neater looking 444 grille. It just attaches with 4 small bolts to the nose section, AFAIK the positioning of those 4 bolt holes never changed.

Changing hood and grille is something I might do if I had the b18 nose and hood laying around, but the b16 (and B4, and B14, et al) nose works just fine on my car. The radiator apparently has enough cooling capacity to cool the larger engine, the admittedly bulky and intrusive arms on the early style hood clear my DCOE carbs. The later style nose and hoods are somewhat better, but the expense and hassle of finding and installing them just isn't there, in my opinion.
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'63 PV544 rat rod, '93 Classic #1141 245 +t