what amperage alt should i run?

Add up all the big power draws that you will need - and rpm.
You can do worst case if you don't have or want to figure out the exact. Worst case being your fuse or circuit breaker.

Headlights, Wipers motor, heater blower and your electric fan could all be running at the same time and at idle rpm.
A CD ignition can pull a fair amount, but more as rpm climbs. So usually less an issue.

The problem is other than a Chrysler original part, the amp ratings of alternators is at an unknown condition. Safe bet it is their max output which means you can't directly compare it to the Chrysler rating.

If your engine's idle speed is fairly low, and you're adding that electric fan, I'd suggest that your odds are better with a 'square back' with not too high of a rating. One way to get higher max output trades off the low speed output. In my experience square backs really do a little better at low rpm than the round backs. Of course theirs no guarentee what's inside on rebuild - that's why I said 'odds are'.