Rebuild questions.

[suprflyusmc1]

I am looking at doing a rebuild. I was reading about the tolerances for certain parts of the engine.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=A&Page=5

what is the significance of the tolerances that read "Mark 1, Mark 2, Mark 3, Mark 4"



Also i'm looking at a kit that's sold by RPMMAchine

http://www.rpmmachine.com/shop/html/Toyota-3.0L-1987-1992-7MGTE-Turbo-Supra-Engine-Rebuild-Kit.html

Any comments?