Go to www.shoptalkforums.com. Look in the Type Four link. Also do a search for topics in their archives. Anything and everything you need to know is there.
If you see a post by Jake Raby, open the info icon and his business site is listed. Check "Jake's Thoughts" and also read what he says about T4's in Replica's.
I believe the 914 is actually a Vw engine, but yes, you can say you have a Porsche engine in your car. Why not. But if you ask me, the other benefits of a T4 make a better argument for doing the switch -- lots and lots of torque, an evolutionn of the T1 package and a long service life. T1 fans rightly say they have more performance options, their engines rev higher, etc.
There is a bit more cost and parts than a straight across bolt in job, but it isn't too bad.
Different stokes for different folks.