Welcome to the forum. You'll enjoy your mid-engine Porsche experience.
You don't need to be in a hurry to change the IMSB. Wait til you do the clutch. 97-99s had a better design than 01-04s. But it's up to you.
I bought a 77 VW conv as this yr's winter project. It didn't run when I bought it in late Sep and it's been in various stages of running since then. Currently in a no-run state. I'm going to name her Sybil because of all her personalities. My plan is to have her ready to sell when the weather improves. She's got good bones, just need her to behave a bit better.