Non Turbo:
https://www.ultimatespecs.com/car-sp...o-940-20i.html
Turbo:
https://www.ultimatespecs.com/car-sp...20i-Turbo.html
The "slowness" will not really be noticeable in the speeds you can crank it up to, although there is 12MPH difference in maximum speed, but rather the time it takes to get there; 0-62 in 13 seconds as opposed to 9.6.
It really depends how you want to be driving a thirty year old car. The only things it really limits are rapid overtaking and nipping out into traffic. Both of these can be avoided with suitable roadcraft.
This said, my current favourite in my fleet is the 3.0 V90 Mk1 I bought during the pandemic because of its effortless power and comfort.
If you are planning on restoring your original Wentworth then maybe look for the same or similar model to buy as a temporary replacement because you will be able to swap parts between the two and keep the best stuff when you've finished.
Alternatively, buy a good 2.0 Turbo with base trim, transfer all the high-end goodies from the broken one and save yourself the hassle of repairing it.
Don't contemplate converting a non-turbo into a turbo. By all accounts it's a total pain to do.