cspracer. It shouldn't require many changes going from 12v to 16v as far as accessories go. Depending on your who makes your switch panel, relay board etc, the only thing I have found was that I needed to change the water pump and fan fuse to higher amperage fuse, again depending on who makes your switch panel, relay board, etc. If you run a K&R Engineering relay board/fuse panel, you won't have to change anything because all the fuses are already high enough. If you run an Auto Rod Control switch panel (which is what I run) then you would need to change the water pump and fan fuse to either 25 or 30amp, I cannot remember exactly what fuse is in mine. But other than changing the fuse, you don't need to change anything else accessory wise.

I would recommend checking the ignition timing in your car after switching to 16v. If you are using a distributor to time your car and are the distributor is not locked in, then you may need to adjust (just from my experience). If you run a locked out distributor and/or crank trigger, you shouldn't have to change timing of the ignition but I would still check it.

As far as an alternator goes, my Powermaster XS Volt alternator (Part #8148) has an adjustable regulator so it can be used on a 12v battery or a 16v battery. The alternator is adjustable from 13.5 volts-18.5 volts. I also did this in the event I ever had to use a 12v battery in an emergency situation, I wouldn't have to worry about needing an extra alternator, or disconnecting my alternator.

I would personally save the weight of the second battery and spend that money on the battery charger from the second battery. Like I said in my last post, XS Power sells a battery charger that can charge 12v, 14v, or 16v, battery, (part # 1005). It is pricey for the charger but again its like buying two battery chargers.

D1600 Battery part number
1005 Battery Charger part number
8148 Alternator part number

Stuff isn't cheap but it's worth it.