I did mine with 5 Bosch style relays (one is a spare) and a 5 position fuse box in the middle of the inside of the firewall. I have A/C, so the right side and glove box are no-gos. Given the A/C, an underdash radio and way too many calories per day into my 6'5" 76 year old body, I wish I had installed it under the hood, high up on the firewall.

I didn't know about these combination fuse/relays when I built my electrical system, but if I do it again I'd use them. The only thing "wrong" with these relays is there is no "normally closed" contact (87a), but I've never needed this in automotive wiring.
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Last edited by Bill Hanlon; 02/16/2023 3:12 PM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.