Frankenstein Build?
 

I just got my hands on a BP4W for 350$ bucks and have already started stripping down a VVT motor that I plan on swapping into my Miata. Is there anything useful in terms of the BP4W that I can use. Maybe match the block with the vvt head or vice versa? I know the BP4W head is the best flowing but I also wanna play with vvt so any of your suggestion would be helpful👍

VVT head flows pretty much the same. Bottom end is .5 less compression, iirc on the 4W.
Some say the VVT rods are weaker, but I think, if it wants snap, sooner or later both will do

Yea, I heard of the lower compression, but this engine is going for a rebuild so all forged pieces so weaker rods won’t matter. So I guess I might go with the BP4W block for lower compression as I am running a turbo and then the vvt head.

Keep the VVT (BP6D) lower end. It has minor upgrades over the BP4W lower end.
It has a half ass main journal girdle and a larger oil pump. The VVT oil pumps flow is needed for the VVT system.

Pistons are what determine compression ratio (at least in the lower end) and your forged parts will determine the compression not what model of block you have.
If both blocks are in decent shape I'd use the BP6D over the BP4W.

Since you have two blocks apart take care not to intermingle the pieces, most are the same but some are NOT. Keep 'em separated!

Keep everything until your build is complete. Try not to use parts from the BP4W if you can as you have a "complete" extra motor right now that is worth more complete.
If you sell anything off that will be the one part you need to finish your build...
Learn from my mistakes...
It's cheaper.

Ok thanks so much! I didn’t know they had upgrades I’ll look into that more