Trying to match your 383 vs any other 383 on the planet is a waste of time. to many variances in compression, timing how clean the block is inside Etc,
Your individual system from the size or volume of your radiator core to the open un-obstructed frontal area to the size & CFM of your electric fan will all play a part in how well your individual combination cools..........
Also things like pulley size and water pump speed , slipping belt , How clean your inner block and water passages are , pressure cap......sometimes your system will just not build or maintain 14-16 lbs......start with the basics, flush the block and radiator, pressure check the system , check for soft hoses that can collapse......add an additive such as water wetter , take the effort to analyze each part of your system and make it better.......
Certainly! And any messing with therostats is just a bandaid for an insufficient system. If actually adequate, the temp should never really exceed the thermostat rating. As for the bleed hole in the thermostat, if the stock bypass in the water pump is functional, not needed.
What worked for me (381 sbc in a flatty):
1) Aluminum radiator. Absolutely superior to brass in the transfer of heat, not to mention 15 lbs lighter.
2) Full, very well fit shroud. I only left a 1/2" clearence for the blades but that will depend on your motor mounts and how much movement they allow and how much frame flex there is. There should be no area of the core that isn't covered by the shroud and it is best to have it ducted so no air can pass around the radiator/shroud.
3) FlowKooler 1880 high flow water pump. I needed the 3/4" pilot so some of their other models could fit your needs.
4) 19" 7 blade mechanical fan. No clutch or flex blades. Yes, this definitely costs some hp and economy but if you really want to move air, it doesn't get much better.
5) 15% speed increase with water pump pulley (this was a sort through the bin at the scrap yard and then machine an adapter),
6) Water wetter-yes they really work, and
7) As pointed out by Terry, an unobstructed air flow. Keep winch mounting low and forget the lights in front of the grill. With a vented hood, the exhaust air shouldn't be a problem but you can open or louver the wheel wells also.
Of all those, I would rate the aluminum radiator tops. That alone was good for more than a 15 degree temp decrease.
As noted above, timing can have a big effect and I would check that before anything else. For a comparison, I'm running 10.5:1 cr, aluminum heads, roller cam, and long tube headers.
