If you decide to do this Tony have a look at this:
http://www.cienega32.com/miata/nb2na...top_xplant.htm
Do check that you need to go this far with the Mk1 though as the captive bolts may be more accessible simply by removing the carpet under the bay where the soft top folds in. Also, have a look at the info about the rain gutter as if you damage this taking the soft top off it has to be replaced.