All that work to end up with what? A replica.

You turn your original Cossie Saff into a 1.6 L logbook wannabee.

Just reshell into a solid Saff Cossie shell, available all the time, there's so many get broken these days. £300 for a non rolling shell seems to be the going rate, more if rolling and bits left on. Plus you can get one with full service history, low owners, HPI clear, good alarm still fitted with paperwork - things could work out very well if you bide your time!