Hi Graham, i hope you're doing well despite all the misery .. :-( ...
So you had an X1/9 in 1973, i can imagine it being a heap of rust and a bad engine ...
My friend got his X1/9 in 1987 which had a Lancia 1500 cc engine. He managed about 100,000 km in 7 years with the car but started experiencing troubles with the engine and the rust began to come in .. .
I received my 1800 cc Jetta Mk2 also in 1987, managed 290,000 very intense km's in about 11 years until the engine started to lose oil .... At the lights up to 130 kph the cars were equally quick, but the VW was a lot faster on top speed.
I don't know much about the TR7, all i know is that i wanted one at the age of 18, but my parents bought me a brandnew reliable and humble VW. ..... sooooo .... i got a black two-door Jetta 1800 .... then lowered the suspension (imported a rallye-set from Italy ... LOL), bought the lightest wheels on the market and fitted GTI-brakes and a GTI front-spoiler. Result was that is was faster than a 112 bhp GTI-golf and cornering-speed capabilities ( 920kg + low unsprung weight and very sticky tires) in combination with a young fool behind the wheel made it as quick as all the 2-wheel (front or rear) drive cars up to a 190 bhp (except from a BMW M3, even a Merc 2,3-16 wasn't that much faster on twisty roads) ....
So , you can imagine why i kept the car until the engine was pretty dead
... . and actually the stiffness of the chassis got a bit on the low side too ... LOL ... .

...
Cheers ... & ... heads up Graham !
Filip