I found a round casting mark on my engine block with the numbers 19758. Does this signify that the block dates from 1975 and is a V8? I know from the PO that the block is not the original.
no, thats not the casting number. here is what you need to look for and what it will mean.
Use this handy chart to decode all of the Ford part numbers. For example a 1968 200 6 head part number: C8DZ-6049-C
The first two digits indicate the decade and the year;
A = 40's
B = 50's
C = 60's
D = 70's
E = 80's
F = 90's
G = 00's
So the first two digits indicate that it is a "C" 60's and a "8" so that tells us it is a 68 head.
The third digit designates the vehicle model line;
A = Ford full size (Galaxie)
B = Bronco (70-75)
C = Torino/Elite
D = Falcon
E = Escort
F = Pinto, Maverick, Late model Falcon
G = Early Comet (61-68), Montego, Cyclone (69-76)
H = Medium & heavy duty truck
J = Industrial
K = Edsel
L = Lincoln (58-60)
M = Mercury
O = Fairlane (62-68), Torino (69-76)
R = Capri
S = Thunderbird
T = F series or Bronco
U = Econoline van
V = Lincoln
W = Cougar
Z = Mustang
So the third digit indicates that it "D" was off a Falcon.
The fourth digit designates the engineering group;
A = Chassis
B = Body
E = Engine
Or if it's a service replacement part;
M = Ford Motorsport or FFRP
X = Original Ford racing program/Muscle Parts
Y = Lincoln-Mercury
Z = Ford
So the fourth digit indicates that it was a "Z" Ford replacement part.
The next 4 numbers (6049) indicates the Ford "group number" for a head
The last digit "C" on the end of the part number indicates that this part was in its third revision. If revised again it would turn into a "D" and so on. When they reach the end of the alphabet they started over with AA, BB and so on as shown in this "example" part number: D7BE-6090-AB.
Our example part number C8DZ-6049-C decodes as;
C8 = 68
D = Falcon
Z = Ford replacement part
6049 = Head group part number
C = 3rd revision