will this fit a 1950 ford custom ?

Yes for the driver's side rear.

I have a 1998 xj, got new wheel cylinders for rear drums. i was supplied the uw17507 & 8, these are for a 10 inch. i have a 9inch, can i use these?

If you can't find the answer you may have to pull a drum and compare the old n new. If they don't match up in size then it is the wrong part. Make sure the piston in the cylinder is the same as well. There are different types of pistons as well. (Where the shoe meets the cylinder) if your drum is not rusted on pulling a wheel n drum only takes a few mins.

Manufacturer	Dorman Products
Brand	Dorman
Model	Dorman W17507: Drum Brake Wheel Cylinder
Item Weight	1.6 ounces
Product Dimensions	4.4 x 3 x 2.4 inches
Country of Origin	China
Item model number	W17507
Is Discontinued By Manufacturer	No
Exterior	Machined
Manufacturer Part Number	W17507
OEM Part Number	134.61006; 135.61006; 18E1342; 18E16; 2017507; 33627; 784-34006; 84-34006; F17507; W-81006; W906090; WC13627; WC17507; 2620735; 3146138; 3196564; 3203311; 3492675; 352786C91; 4088893; 4713349; 4761749; 4761749AB; 52000849; 8952000849; C20Z-2262-B; C3AZ-2262-B; C4TZ-2262-A; C60Z-2262-A; D2ZZ-2262-A; D3TZ-2262-A; D3ZZ-2262-A; J8126715
Position	Rear

W17507 Rear Driver Side Drum Brake Wheel Cylinder Compatible with Select Models

Description

Specifications

Common Questions