I do a very long drip acclimation, possibly overkill, but I do think clams count as some of the most sensitive inverts (for water chemistry). I put the bag with the clam inside of a 5g bucket, and then slow drip (1-2 drops per second) for 1.5-2.5 hours, with a small heater in bottom of bucket (outside the bag) to keep it near tank temp if ambient temp is much different. Basically enough to flush the bag volume a couple times over.
Then if it's a sufficiently healthy clam, I take out of water, and toothbrush the shell staying clear of the byssal opening and hinge, covering byssal opening with finger if need be. Also inspect for pyramid snails or other pest looking things. If it's not healthy (byssal opening looks sunken in which means its body isn't full / it's starving or injured, or seems to have a hard time holding itself tightly shut), I just visually inspect without brushing.
I usually drip for hours, as there is no harm in doing so, but going too fast can definitely cause stress. Salinity and pH swings are the biggest factor when acclimating them (and most inverts), so slow is preferred.