The Ebay listing for that blue GT4 stated it had 345/45-19" rear tyres.
They are not 45 profile, but 35 profile.
I have very similar set I made for my car.
Front: 285/40-17 Bridgestone on 17x9.5" three piece rims.
Rear: 345/35-19 Bridgestone Scuderia on 19x13" three piece rims.
You can purchase the tyres from tire rack in the USA at good prices.
Heres a picture of the massive rear:
regards,
Tony.
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.