I would think there should be 4 separate holes otherwise it would defeat the purpose of the 180 degree design.
I would want the mufflers supported to prevent metal fatigue due to their movement. Although from your pictures I don't see an easy way to do this.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.