I have a Be Cool aluminum radiator in my 68. The engine (ZZ4) runs cool, at approximately 180 degrees F. I've read a lot of De Witts postings where he cites the quality of his "Direct Fit" radiators, and so for my 70 BB, I plan to buy a De Witts. With fans, you're looking at approximately $1000.
The Be Cool radiator was physically. a direct fit. However the radiator has a fill cap at the top of the radiator....this is a standard radiator configuration, however, it's incompatible with the radiator cap in the 68 overflow tank (the mini-beer keg tank). I disabled the Be Cool radiator cap by cutting off it's internal spring, so now the standard 68 radiator cap in the minibeer keg overflow tank is the functioning cap.
To power the fans and electric fuel pump, I bought a higher capacity AC Delco alternator. It's illustrated in the GM Performance Parts catalog. Since the 68 alternator is externally regulated, and 69 and up alternators are internally regulated, I just disconnected a wire (or two) going to the external 68 regulator.
I'm a member of the school that doesn't think single wire alternators are a good idea. Lets say the internal regulator is set at 14.2 volts. The single wire alternator then sets the voltage at 14.2 volts inside the alternator, so with heavy amp flows, and wire harness drops, the voltage actually delivered to the accessories is less. I have a center point source terminal on my drivers inside fender. This central point feeds current to the fans and pump. With a two wire alternator, the second wire is a voltage sensing wire. It's attached at the center point source terminal and hence maintains the voltage at 14.2 volts at this terminal. The voltage inside the alternator is therefore a little bit higher. (Knowledge and parts for changing the 68 wiring was from M.A.D.D electronics. He may be out of business now.)
I have a mini-starter that's illustrated in the GM Performance Parts catalog. It works great. Maybe 1/2 the weight (less) that the original starter.
I buy my stuff from Summit. Order in the morning, it's on my doorstep late the afternoon of the next day. Don't know how they do this so fast.
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One last thing (I'm really wordy today). It's really hard to make extensive changes to your engine wiring harnesses and keep it professional looking. (My wiring harness had to incorporate a HEI distributor also). I used OEM style connectors from Packard Electric. The problem is that if you want a particular 4 pin connector, you have to buy, say, 25 of them. Need a two pin connector? 25 more. Also, to install the connector pins, you have to buy the pin crimper tool ($$$). The pins come in bags of 100, even though you need only 1/2 dozen. And you have to buy different pin sizes for different wire gauges, and of course you have to buy another crimper. I used different colors of wires in my new harness build up...this was probably a mistake. The different wire colors are a visual distraction. Next time I think I'll use all black wires and just document the wire identities at each connector pin. One last thing. I bought a new 68 repro harness for Lectric Limited. My new harness was built so that I didn't have to modify the really beautiful 68 harness.
