Short span lintel under house

I'm planning to install ducted heating and will be running two large ducts down a passage way under the house. With the current clearance once installed the ducts will block future access into the passage which is the only way to get under the house. I would like to install a lintel and remove some of the sandstone and brick to give more room like below. Lintel in red, area in green to be removed.

The wall is single brick, can I cut out half of the mortar on one side and then hammer in a steel angle?

Any advice?

http://www.renovateforum.com/attachm...se-passage.jpg


On the other side of the passage it looks like they have used a piece of floor board, ha

http://www.renovateforum.com/attachm...-passage_2.jpg
Attached Thumbnails http://www.renovateforum.com/attachm...se-passage.jpg http://www.renovateforum.com/attachm...-passage_2.jpg



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