What to do? Keep it, update it or leave it alone?

Greetings to all!
So here is the issue at hand. I've got a 1990 348ts that has 85k miles, but new paint and interior. Suspension is sound, but engine and trans could use updating. It runs well and strong, does not leak or burn oil, just lacks the HP of newer cars and the trans it's a 5speed and could use 6 and has the issue of 2-3 gear shifting problems.
I've thought of selling, but the offers were Way To Low, I'd rather give it to the kids or make it a parts car for the prices that we offered.

I'm looking to downsizing as the wife has a1996 F355 Spider and I would prefer to have only one Fun Car, such as a 360, 430 or even a 458 Spider.

So any ideas out there? What course would you take? I like the looks of both cars, but don't need or want to care for two and retirement is less than 10 years off and I'm looking to get things set now so as to enjoy and travel and not at working on vehicles.

Look forward to the responses.

Cheers!
Roger
Elko, Nv.