Ford festiva spl car

Before you laugh those of you who know who i am know I am going to do something sick with this car. I just purchased a 1992 ford festiva. i still wince at this but it was $50 on ebay. I was wondering if anyone knows the size of the stock alternator and anyone who makes one to replace it.   I am figuring i will need to weld brackets and put a diffrent alternator on it unless i can find a stock replacement with higher output.   I am debating 6 15's 9 12 inch squares or 12 10 inch subs   this is going to be a slanted wall from the b-pillar to the rear window.    but i know power is going to be a difficulty..let me know what you think and what you can help with

i wouldnt do a slanted wall if i were you.  i do alot of SPL competition.  i would also definitly use 15" subs with HUGE slot ported box.   i would do a str8 wall, no slant.   good luck with the project.  competition is alot of work.  i just won the state record this year.  im already working on my new project, hopefully ill get the record again.