I have heard good things about them.
As an alternative, if you;re rebuilding your 390, I have a spare pair of 428CJ heads, a spare CJ crankshaft that would add some beans to the mix.
Your existing rods could be used, get a set of 410 pistons for the extra stroke, and a nice light 4-barrel intake manifold and you'd be away (a little faster than before...)
Food for thought, no drama if that's not of interest...