D47U track replacement

hello bicicat , The d4d and the d4 6-7u both use 6.75'' pitch ,but there are a few different bolt sizes and bushing sizes ,if you can get a part number of the links ,i can give you better information ,bruce oz

Yes .. but there are qualifications involved ..

1. Cat have continually modified the undercarriage on every tractor since the 1930's. Every "improvement" results in .. higher rail height for increased life .. deeper hardening .. thicker sections to improve strength .. often, bigger shoe bolts .. and sometimes, heavier bushings ..
Every time, a new and improved, undercarriage design came out, the previous one was deemed "obsolete" ..
The list of link/chain part numbers that will fit your tractor run into probably a dozen or more.

2. Any D4, 6.75" pitch undercarriage will fit your tractor. However, with the "dry" chains .. there are 1.99" diameter and 2.12" diameter bushings, that require the sprocket to be changed if you are moving from the small diameter bushings to the large diameter ones. The rollers don't need to be changed.
D4D undercarriage will fit .. but, the D4D has bigger shoe bolts (5/8") and much higher rails with heavier thickness links ..
The D4 track chains originally used 1/2" shoe bolts .. then 9/16" .. then 5/8" diameter, shoe bolts.

3. There are track chains with dry links .. then there are chains with dry "sealed" links (these have the two disc-shaped washers to prevent dirt ingress into the pin and bushing) .. and then there are the later "sealed and lubricated" links (SALT chains).

The dry links were in use up until about the late 1950's, when the "sealed" links appeared, as a design improvement, to extend undercarriage life.
The SALT undercarriage appeared around 1970-1971, depending on the tractor model.

You will find link P/No's that are dry "unsealed" links .. and link P/No's that are dry "sealed" links. Sealed Cat links have the word "sealed", forged on them. They are not interchangeable when it comes to pressing them together, the "sealed" links are machined to accommodate the seal washers.
You can mix/n/match the dry "sealed", and the dry "unsealed" chains, but the "sealed" chains last longer.
If the chains are SALT chains, you are into a whole new ball game again.
Come back with P/No's on what you currently have, and what you want to install.