it'll fit, but for the amount of work, new would be better and original would have been 10", possibly 11" .... and FYI. the 3700 model is a forward control van, what your pics show is a 3600 3/4T pickup as indicated by the 36 on the fender emblem

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics