I have a Shimano Calcutta 51, the reel seat im not be able to mount the reel on most of my baitcast rods cuz of slop. What I mean is the reel will slightly move sideways on the reel seat.

 

I've tried adding electrical tape to the slightly narrow reel foot. This kina helps but the reel still moves when reeling. 

 

Is there an aluminum or something I can slide onto the reel foot, front and back to stop the side to side wobble? I love this little reel, I've had it since 2005 and it's now a classic. 

I don’t remember if I  have that problem with my old Calcutta 50, but definitely not with Conquest 50. I’m gonna try to mount the reel with other rods to see if I have the same problem.

Do you have any reel foot stickers (come with some old reel)? It might help a little.

Some reel/rod combinations do that, I just use painters tape.

Tackletrap has this reel foot protector for sale. It usually comes with high end reels. 
https://tackletrap.com/index.php?main_page=product_info&products_id=17967

 

 

I use the stiff clear plastic from blister packs and fashion my own for one particular spinning rod I own that has a little slop with any reel I try on it. That works to keep it from squirming. Other than that, although I LOVE the rod, but I will never buy another or recommend one to a friend because I HATE that squirm when setting a hook or fighting a fish.

You could make a plastic shim cut out from a water bottle. Easy to do. 

5 hours ago, Dwight Hottle said:

You could make a plastic shim cut out from a water bottle. Easy to do. 

I shim my old chronarch 100A’s with old credit card cut outs. 

Self adhesive medical wrap is great for this.  It's a cloth tape that only sticks to itself and doesn't leave any residue behind.  Alternatively, heatshrink tubing also works good.

 

I just buy rods with good reel seats

Use strips of beer cans.  Aluminum won't deform like soft tape and other plastics.