Compact twin smoke unit

The part number you've quoted is an AC-12 funnel, not a smoke unit, designed for use with one of the dual chamber Legacy smoke units that has whistle steam. That smoke unit looks like this (part number 610-1462-200):

Those units won't produce full smoke out of both outlets unless the whistle steam function is activated. I'll be corrected by someone more expert if I am wrong but I don't think that those can be retrofitted into a 6-28077 Lionmaster Challenger, which comes stock with one of the older 27 Ohm Lionel TMCC smoke units. 

Does the part connecting the smoke unit to the stacks on your engine look like this? 

Lionel have made a big variety of smoke funnels most of which are designed to fit specific engines depending on where the smoke unit is placed and whether (as in older models) it's mounted on the chassis or (as in new units) fixed to the boiler/body shell instead. Some, like this one for the FEF-3, have dual outlets that fit into a dual stack arrangement:

But these are attached to a single chamber smoke unit and I think you are after something else. The only engine I can think of that has a smoke unit designed to feed dual stacks individually is the VL Big Boy. But that's a Legacy-based system and I think requires the system software to run. 

Yeah, you are right I meant the 200 unit. My smoke funnel is shaped like the 210 unit you pictured above. However, I was going to drive the smoke unit using either super chuffer(s) or directly off of track voltage in combination with the chuff signal such that one stack would steam in time with the chuff and the other stack out of time. Just want to avoid buying a smoke unit that won't fit. I feel like I saw a smoke unit with a regular stack and an elbow for a whistle steam effect that looked smaller than that double unit.