Here's a good source for them, maybe you can find something:
http://www.stausaonline.com/product-...t-truck-tires/
To me, the STA Super Traxion is a GREAT mud tire for our trucks.
Another source:
https://www.nebraskatire.com/light-truck
I like the Power Kings for mud tires.
Also, since you mentioned you're only going with 8" rims because of the disk conversion, you could search for some 71 or newer K5/K10 wheels (assuming you are still 6 lug) - they will clear your disk brake conversion assuming stock size calipers and can be had in narrower than 8" wheels - will give the skinny mud tire look you seek.