I put a similiar post up on here a while ago, there is a diagram knocking around with dimensions for Subframes, I also believe it is in the Haynes Manual.
My Subframe was in a similiar state as yours, worse in fact and I have refurbished it, it took me the best part of 3 months so if time is of the essence then maybe you should get a new one.
Before you make any decision on buying a complete new replacement or second hand, power wash yours and have a good poke around with a screwdriver looking for weak / rusted spots.
What are the Trumptes and Rubbers like, if its in a bad condition the Trumpets will be siezed into the rubbers and the rubbers will be siezed into the Subframe, lots of WD40 and patience to remove them, don't force them though or you will break either the Trumpet or the Subby.
The Skid Plates that you have scraped and found cracks and rust in can be replace, I made my own but they can be bought for about £12.50 each.
The Minispares complete Subframe you linked is probably worth the money especially if you subscribe to this Forum you'll get 10% discount, but at £1400 that's a big spend when you could buy a pretty good condition second hand for about £300 complete however it would probably still need cleaning up and painting which could cost you another £200 or so depending how you want to do it, shot blasting / chemical strip, galvanise and Powdercoat or POR 15 or like me, hand scrape to bare metal, Epoxy Prime and Top Coat.
