Ok, The two bases that you have already started are the MKI & MKII Bases.
The base that does not have the Guide post is the MKI Base i gave you, The one with the post, and the I cast near the engine mounts is the MKII you first started with (right back at the begining!)
The new base, from the coast is a MKIIIB base, it was cast in the same mold as the first series of VC-160 Auto Drive, But does not have the cut out for the belt to pass through, however it does have the spacing for the belt to run around the pulley, and other casting marks for the Auto.
There is another type of base, the normal MKIII, or MKIIIA, it has the same engine mount area (no belt space) as the first two, but is a MKIII base. I have one here for you.
The MKIIIA also had a slightly different cowl to the MKIIIB, the MKIIIB has a smoother lip around the hole for the starter, While the MKIIIA cowl, is the same as a standard MKII Cowl, wich still shows casting indentations for the starter cover used on the MKI
