What kind of single coils? Fender Strat vintage-style singles are a fiber/felt kind of base, modern ones plastic, Telecasters have metal plates, as do P-90s.
ive used the fralin and callaham plates and didnt really notice a difference between them
I went with a Fralin for my Squier CV 60s Strat. Adding the baseplate gave me what I wanted out of the bridge pickup. And I was looking at swapping all of them out too. But the stock pickups are not bad at all. Glad I went this route.
I'll have to try this with my CV 50's Strat. The bridge is just a hair too bright.
While you're in there, change the pots to quality 250K and put in a .1uf tone cap. You'll be glad you did.
Now and if generic thoughts have any interest:
While we're on the subject, does the material matter? Copper, brass, plated or unplated steel, zinc-coated steel?