Best way to tackle this job?

You need a pulley set. Your Alt. Should wrap around the water pump and crank.

I’m a bit late on your weekend for this job but here’s two worthless cents;

Remove the stock exhaust in full.
Remove the P/S box (& pump) and finish the swap in full.
Resume header installation.
Do not touch the braking system until the header swap and exhaust if done.

Follow Doug’s instructions on installation. If you can not lift the car very high, I have found advantages in an engine hoists use for lifting/tilting the engine.

Best of luck with the car, best wishes on Dad.