Welcome to Team Talk and congrats on a great looking boat.
A couple quick answers :
You most likely have a 351W, although some came with a 302.
Top speed should be about 44 or 45mph
There have been lots of discussions about which oil to run. Do a search and you will find lots of reading. I use Valvoline 20w/50.
I would replace the tracking fin. Not much flexibility there.
will become a great source for parts and info. Get a catalog ASAP - it will become your go to book.
Search for gel-coat threads - again lots of reading. Pretty simple to do if you have some patience.