The engine looks like a Bristol Pegasus/Mercury, nine cylinders, around 900hp. The arrangement of the tappet covers and the head finning looks right, and is quite different from P&w or Wright engines of a similar era. It's a long shot, but the Pegasus was fitted to the Swordfish, so it may be a WW2 relic.
The structural remains look like bits of a steel tube fabricated spar or fuselage, possibly an engine mount, as it is too solid for most of the Stringbag.
Dick