Restoring this old Plus 4 is theoretically possible -- I've seen bigger restorations. But it is always more expensive and time-consuming than expected. The good thing about restoring the TR-engine Plus 4s is that all the parts (or superior substitutes) are available.
Before you make any decisions, you need to determine the chassis number, or at least the year of this car. Hopefully you can follow JCK's advice and find it. If you can't find the chassis number we can determine the date within a year or two by the width of the car, instrument layout, etc.
