my s1 was rotten as a pear, and i chose to do it 100% original and stock, mostly as i was on a tight budjet.
In hindsight the amount of welding and prep i did, i should have cossied it.
unless your going to do an amazing no expense spared resto (which could set you back 10k, with paint as well) then id go for a cossie conversion.
when i sold mine, there were so many things i regreted i hadnt done as i wanted or spent as much as i could have. and this reflected the price.
I doesnt matter how clean the car is, if it hasnt got a wad of history, low miles and a distinct lack of unwelding, then it wont command a high price anyway!!
as you need to cut the floor around, you may as well make it to fit a cossie box.
there were two brothers in 'Fast ford' or performance ford a month or two back who had 2 identical S1 cossies, worth a read if you can get hold of the back issue.
and also if im honest cossie ownership is not the be all and end all. I got 10 times the buzz and excitement driving my S1 around than i do my escort cossie!

and it seemed the S1 was also more of a head turner?
heres my old girl a few months before i sold it with a few bits still to finish off like adjusting the bodykit- 3.5 years, bare metal, painted underside, weeks and weeks of welding, new front ineer wings, outer wings, front valence, crosmember, bonnet, rear arches!!!! full resto.
In fact my mk1 in the pic, id did original, i should nave put a V8 in
My 1949 beetle, i did original, i should have put a scoobie 2ltr turbo in
are you seeing a trend here

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Please dont do what i did, i put in so much work and it was SOOOOOO clean, i ended up not driving it!!! wack in a cossie lump and abuse the old girl!!!