What piston would you suggest going with?
Without knowing a lot more about your deal, I'd be reluctant to make any specific recommendations.
Any of the major manufacturers makes good pistons in cast, cast hypereutectic or forged- I would contact them with all the specs on the engine including how you will be using it and let them make their best recommendations.
Then, shop around for the best prices for whatever piston you decide on.
Wiseco Speed Pro TRW Sealed Power Keith Black Silvolite would be a start.
That said, there are "lesser" brand pistons out there that may
fit your needs (Badger pistons, for instance, used to be fine by me for a plain-vanilla cast piston), but remember- the piston is a highly stressed part that makes expensive noises if they go south.