by Tim Palmer
I'm sure you have often pondered one of life's better bigger questions… Are all engine skid plates the same?
The answer is no. From what I can determine there were at least two. 60-63 used 6257796. 64-69 used 3839263. 3839263 was also used as general replacement after 64 probably, at least my 69 parts book lists it as such. So what is difference? The difference is in the arc cutout for the crankshaft pulley or harmonic balancer. With a harmonic balancer extra space was needed for the fan belt, which means the arc had to bigger and lower. The earlier skid plate can be used with a harmonic balancer but the belt is tough to get on. The parts book lists both parts numbers, but not at the same time. Apparently the later skid plate became a general replacement for the earlier skid plate since the extra space did no harm.
by Gary Baxter
There is an easy way to tell whether a rear skid plate is for a '60-63 engine or for a '64-69 by the holes in the rear face. The '64-69, which has the larger fan belt clearance radius, just has the four holes required to fit over the rear mounting studs on the engine. The smaller radius, '60-63, has a fifth hole located in the center just slightly down from the radius. As to the purpose of this extra hole?