Ok I'm going to try and help you out here.
First off do you have a gsr crank from a b17 or a b18c? Big difference, the b17 crank is 81.5mm stroke the b18c crank is 87.2mm of stroke.
You won't be able to use the b17 rods with the b18c crank. There's nothing wrong with using the 87mm crank with the b16 block but you would need to buy new rods to the specific size you would need. Also the piston size will depend on the rod length.
I'm all for using stock honda parts to gain power so don't think this is a dumb idea. H23 cranks are used in B18 blocks a lot for extra displacement, just have to massage a few other things to get it all working smoothly.