These are the links that deal with the Type IV conversion and some parts suppliers that have stuff you might want for the conversion. If I can I will give my recommendation and thoughts on the different sites and parts places. And if your site deals with this conversion, use the form at the bottom to send me the link.
http://www.cbperformance.com/ - Great parts place. I got my Linkage and Manifolds from them.
http://shoptalkforums.com - The forums that I go to for help and info. The only one that I have found that has a T4 section. Lots of good stuff.
http://www.geocities.com/~dfarr/4into1/ - Good page chronicling the installation of a 2.0 T4 into a Ghia. It shows some of his expenses, some pictures, and some links.
http://www.ahnendorp.com/ - B.A.S Ahnendorp, Great parts site based in Germany, mainly famous for exhaust stuff I think
http://www.aircooledtech.com/type4_upright_conversion/ - Nate's Aircooled Tech, Awesome site on the conversion with good pics and tech articles.
http://www.geocities.com/MotorCity/Downs/2691/type_4.html - Jan's Type 4 Conversion, Not much there, has a couple links and some other stuff
http://www.nextgen-usa.com - Next Generation, This is the site of Joe Cali, the guy who put together the conversion book you should get if you are looking into this conversion or any other
http://www.mattandleah.com/Type4.html - T4 conversion going into a Thing, pictures and chronicles of what they have done
http://www.tunacan.net/t4/index.shtml - The Best site for info on the T4 motor and conversion stuff. Has info on heads, cases, cranks and lots of other stuff. Also compares to a T1 motor.
http://www.dolphinsci.com/typeIV.html - Some good pictures of a conversion motor that used a Down The Middle Shroud (DTM)
http://www.qtm.net/~persoj/ - A personal page about a conversion that they did and some info on the conversion. Used to have some videos of them driving, but I can't seem to get them to work.
http://www.aircooledtechnology.com/ - Raby's Aircooled Tech, the foremost T4 engine builder (that I know of), also does the DTM shroud
http://www.aircooled.net/ - Aircooled.net, Carry some stuff for the T4, great place to buy from, some tech stuff, you should try here first
http://www.webcamshafts.com/ - WebCam, this is the style cam that I bought for my engine from Aircooled.net, haven't fired it up yet but should work great.