305 with 4-speed auto at 148k miles

What would be the good/bad of putting a shift kit in? Car's shift points for 1st and 2nd reminds me of when you had a bad detent cable in the old days.

But when you get on it, it will down shift without issue.

I'm guessing one bad would be the potential to blow out the tranny; given it's age/mileage.

Thanks in advance,

Steve C - RI