An overflow tank is nothing more than a catch can with a hose in the bottom and open to the atmosphere.
An expansion tank or header tank is pressurized with the coolant system.
In Nick's pic, the moroso label is on an expansion tank but there is an overflow tank right in front of it.
The fittings at the base of each radiator cap would tee into the overflow/catch can.
I don't know what you mean by mixing manifold. If you are talking about reversing coolant flow through the head, many have done so. Just bear in mind the system as designed works great and may be no better reversed, despite the claims.
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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS
viewtopic.php?f=5&t=13225&p=134742Simple Spring select
viewtopic.php?f=5&t=11815LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12