Mario, I would guesstimate that if you go the full deal and get someone to do a full body off restoration, replacing/repairing chassis, fixing panels, respray etc, then at least £15-20k I would guess £5-6k of this would be parts and or refurbishment. Rest labour.
Best way is to list all the things missing or that need replacing, and price them up. It take a garage about 2-3 weeks work time to do body off and chassis replace, obviously elapse may be longer as things go away to be fixed. However if you take the hourly labour rate and have 40hours a week you will need roughly man hours times the hourly rate plus taxes. Over here it would be about £80*120 equal £11520 plus tax.
Hope this helps, why not talk with a restorer or good Mog dealer for a quote
