We know of two Firestone Heater cores used in the F Series Ford trucks.   They are quite similar.  Both fit the Firestone boxes.  Both have 5/8" tubes that pass through 7/8" holes that are 1-3/8" center to center however the difference(s) llie in the height of the tube from the base and the length of the tube from the furthest side. 

Because we are not gamblers, we require you send your pattern in.

Picture shows a housing and a heater core.  We do NOT make the heater box housings but we do make the heater core

We make our own copper cores and fabricate our own tanks so, naturally, we get asked to build custom heater cores or "small radiators." Some modern Fords leak like a sieve so we make a copper alternative.  

Present Lead times.

Made in the USA.