This is funny. You want to show your friend that a Bronco can be a pre-runner... The term "pre-runner" has been hijacked by asshats in rangers with no imagination. What is a pre-runner? Nothing more than what you PRE-RUN the course in, in comfort, to preserve the race vehicle for race day. If he gives you crap about the bronco not being a pre-runner, ask him to follow you on a trail of your choice in his truck. Two different animals.
As stated, the wheel base will limit your highspeed off-road stability. BUT... I have seen a few very well designed and executed broncos do extremely well in these conditions. Stretching the wheel base will cost money and I think it could be better spent on a properly set up suspension system. I do not think four link set ups will be cost effective. But if you save up to dump about $2000 in each corner up front and $1000 per rear corner (front coil-overs with bypass, rear leafs with bypass) you will have the capability to keep up with him, if not pass him.
It's not all the cool stuff you use, it's how you use the cool stuff.