You don't need the purple wire to the starter, jump it to the pos cable post, and use a remote sol, like the hot-start fix does.
Junction block, there are many to choose from, and if you really wanted to get trick, you could use a modular fuse block that incorps maxi, ATC/ATO, mini, and relays, all in one. The basic stud type is what I think you would be best with.
Source, again, many out there, here's some of who I use:
http://www.delcity.net/
http://www.wiringproducts.com/
http://terminalsupplyco.com
http://www.trickcableandswitch.com
http://www.techflex.com/ (expandable loom I mentioned)
As for the splice under the dash, replace it with a stud type distribution block, will give you more flexibility.
Attached are some of the pics from my stuff over the years, might give you some ideas.
Another suggestion, if you're going to upgrade to an internal alt, use a CS130, or better yet, a CS144.
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1970 GTO Judge Tribute Pro-Tour Project 535 IA2
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1971 Trans Am 463, 315cfm E-head Sniper XFlow EFI, TKO600 extreme, 9", GW suspension, Baer brakes, pro tour car
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