I would look at it on a cost basis and start looking for a 2nd hand lump as it will be way cheaper than rebuilding yours, plus a swap is diy territory and you can play and learn on the old engine at your hearts content and have loads of spares to boot.
A dirty bodge is to do an oil change and run it on nice thick 20/50, I recently read on another forum where a guy had a really shagged engine, so shagged it smoked like a trooper and had low oil pressure, so he ran it on 85/140 gear oil and did so for many miles/years!
