IT 465 Expansion Chamber?

I just picked up an '82 IT 465 that needs a few critical items. They are proving very difficult to find.... I got a line on potential '81 YZ 465 chamber to replace the crushed and cracked one on the bike.

Wondering if any can tell me if an '81 YZ 465 chamber will fit an '82 IT 465 chamber and stil use the stock spark arrester?

Thanks all,
Bernie