I have a red '81 in pre-project phase. Though it is gutted for the most part. Can't help with a windshield, mine's cracked around the last couple screws on the stb side.
Yeah Teleflex recommends dual cable for speeds over 55 but that's probly a lil conservative. If you do go that way I don't think you'll have to modify the splashwell, since all you're doing basically is adding another cable? Jerry might be able to answer this question.
Sounds like the trim cylinder's leaking internally, shouldn't be a big deal. Probly a seal/O ring on the piston(s).
Yes that's a nice looking specimen you have there. Love to see some interior pics. I'm basically starting from scratch. Whuddya got pushin it?