TB question?

I have the stock TB on my lt1 with a p600b and it dynoed 400rwhp and I was wondering if I should go with a 52mm or 58mm TB. I was wondering the gains I would see and if I needed to go with 58mm. I doubt I will be upgrading my blower at least for the time. I just wondered if the 58mm would be worth getting or just go with the 52mm.

At the most, I'd go 52mm since the intake mouth is 52mm. I don't forsee much of a gain with a bigger throttle body.