Is this what you are working on?
http://chevy.oldcarmanualproject.com/parts/1929_54/089.htm

The cam gear and crank gear are marked, they must be lined back up when assembling. Rotate the crank till the gears line up so you know what you are looking at. It should be two little dots on the gear teeth. Once clean, paint a bright color dot on each for easy alignment.
See here;
http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0607.html


Unbolt the main caps, be sure to keep the bearings with each cap and keep any shims that might be with them. Keep each bolt in the cap incase there is a different. Keep the caps in order, THEY WILL NOT FIT OTHER POSITIONS.

Cam will come out after removing the two small retaining bolts behind the cam gear. You have to rotate the gear to get to them. Pull cam first.

Go here and get a copy of a shop manual for your truck, most all inlines are the same so get close if your year is not listed.
http://www.oldirononline.com/
http://chevy.oldcarmanualproject.com/index.htm

Here is a good link to a 250 cu in inline six, http://oldcarmanualproject.com/manuals/Olds/1966/Chassis/06-Engine.pdf

Joe

1937 Chevrolet Inline-powered Streetrod