I would say z-fever for vq/vg series engines. They have spent over a decade mastering the z motors/chassis. (will be a tad expensive but you are paying for the expert's masterpiece)

if you were doing a 4cyl to the hilt I would suggest xat or enjuku as they both have built bulletproof ka's and sr's (not for the man who holds his wallet tightly)

if stock motor swap (which you are not doing) or looking for parts (again not doing) I would recommend DC as they have a collection of parts on hand and provide a quick turnaround.