Blue/Red Top differences

[zzgasoven]

I'm confused about the differences between 4AGE Blue- and Red-top engines.

Blue-tops produce 130bhp max. and 149Nm torque max. as standard
Red-tops produce 120bhp max. and 142Nm torque max. as standard

(coudn't find lbs.ft torque value anywhere, 149Nm means nothing to me!)

Despite the red-top being stronger, its less powerful / has less torque?

When I rebuild my engine, what should I do -

Blue-top head and block
Red-top head and block
Blue-top head and red-top block
Red-top head and blue-top block

Yours, confused of Swansea!