As scoutboy mentions there are many variations of the sv engine used across the entire spectrum of products that were produced in all divisions of ihc.
In the case of your loadstar, if the engine and peripherals are original, it has two distinct differences regarding the lubrication system.
1) while it uses a spin-on type oil filter that bolts to the block in the same manner as any Scout or pickall, it is somewhat different in that it mounts the filter can in a straight up and down orientation. Due to vehicle component interference on non-loadstar apps, it's not possible to use that filter system without some vehicle modifications in most cases.
Also, the loadstar filter is approximately twice the overall length as the common spin-on filter used in light duty vehicles and is roughly two quarts oil capacity instead of the more common one quart capacity.
2) the loadstar oil pan is significantly different compared to either a Scout II or a pickall pan. Depending upon the actual medium duty truck the engine is in, it could have a front sump oil pan, or a rear sump oil pan. And either of those pans hold approximately four additional quarts of oil as compared to either Scout II or pickall. Consequently, the oil dip stick is calibrated only for the much deeper/higher capacity oil pan on the loadstar.
Front sump pans (most common) have the dipstick mounted in the front of the block. Rear sump pans have the dipstick mounted through a hole in the side of the pan, similar to the pan used on a Scout II, and the hole in the front of the block for the dipstick tube has plug pressed in to blank the hole.
Until you verify oil capacity by actually adding oil until the "full" tick Mark is reached on the stick, there is no definitive answer to your question because we don't know which oil pan your engine is running! There appropriate medium duty service manual is no help in this regard since all sv engines could have had so many different oil pans, filter systems, etc, installed it's impossible to give a "generic" fill. However, that information would have been contained in the owner's guide for your 1700.
I have pictures comparing the loadstar oil pans and filter sets with similar items used in pickalls. But dam if I can locate on the hd! When I finally run across 'em, I'll post, the loadstar pan is significantly greater capacity.
Right now, for an oil and filter change, and if you are using the double length filter, I'd dump in 8 quarts and then crank the motor to pressurize and leak check, then shut it down, and add additional oil until ya hit the stick Mark.