I'd recommend Clifford™ on my experience alone, but I'm not the resident expert by any means.. h:

The major things to look for are the systems used to detect entry, and I'd also recommend an auxilliary siren with it's own battery backup system. A starter kill feature would also be advisable...

It depends on what your investment in the vehicle is, and also - since you're putting in an alarm - seeing what your insurer has to offer in terms of discounts for various levels of security systems...

My DC4 came with an aftermarket alarm system, but I haven't researched systems in any meaningful detail since about 1998..h: