The following link works, and has always been accessible:
http://www.ht4100.com/The problem with swaps in these cars is that you can't really get the ECM to work correctly without all of the proper inputs. Since the trans, cruise, and climate control is operated by the ECM, what most people do is get their 4100's rebuilt, or get a Jasper replacement.
You also need to replace the oil coolant lines and radiator to maintain the Jasper warranty.
The problem is that the value of rebuilding and installing a motor far exceeds the value of the car, unless it's an 84 or 85 convertible.
It's a real shame that Cadillac saddled us with that motor because they are some really good looking cars, and could have been very useful as an entry level collector car, but that motor gives people a bad taste.
I have owned a bunch, and still have an 85 Eldo convert.
If you can find a nice 79 or 80 Eldorado you can retain some parts, and sell off a lot of other parts on ebay.
I found, and paid a lot for the 80 convertible shown below, but in 1980, Cadillac was using a "real" Cadillac engine. Not one of their best, but it's a 368 all steel engine, in the same family as the 472/500/425, and any of those can be a bolt in swap.
Good luck in dealing with this.
Brian