Atlas/Soundolier makes relay banks in 2,4,or 8 banger configurations. The 4 relay unit is about 5"x5" footprint. Their stuff is for 24VDC, but you can order the terminal base/relay socket units sans relays. The sockets follow a standard relay footprint, and you could get 12VDC relays from another source.
Check out www.atlassound.com, and check the "IR repeater, pwr supply, accessory page.
Everything you mentioned is under the hood, and many newer cars and trucks have relay banks for these under the hood. I would suggest going that route, as it woould be real easy to remove from a donor, and easier to implement under the hood, rather than under the dash.
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