if its a in line 6 its a 300ci------ if its a v-8 3to 4 options 302small block 351w still a smill block 351 Cleavland big block 400m or 460ci......
http://www.fordf150.net/howto/decodevin2.php
Use the VIN Decoder to find your motor if you know it is either the original or was replaced with the same size. The 4th character is your Engine Type.
As to the previous answer, correct me if I am wrong but from 1973 to 1976 the "H" code was for their 390cid.
You didn't mention what size engine you have but, if you follow the positive battery cable from the battery it will lead you to the starter relay, then to the starter.
Size 15
WHAT IS THE TIRE SIZE ON 1953 FORD 100
what is the rim bolt pattern for 1978 F100 xlt
30x9.50R15
Assuming you have the 4.9 (300 CID) engine, it takes a group size 56, 550 CCA.
72litres
15 inch
P235/75R15 (Factory)
235 x75 x15
5x5 1/2
235/75/15 is the size on my 1966 f100