They are also very very prone to overheating - and to gasket blowing
A sample of one is not necessarily reliable, but our 1380 has done neither of these in 30,000+ miles of road and track day use, and the engine had already done 10,000 miles with the previous owner in a different car.
The only problem with overheating came when I removed the by-pass hose, so it went back. It has a high capacity water pump from MiniSpares, but fitted with a large diameter pulley to prevent overspeeding, and I also run a permanent flow through the back of the head via the heater.
Crawling for 3 hours during the Lord Mayor's Show parade a couple of weeks ago, followed by a track day at Goodwood 2 days later showed exactly the same water temperature range (170°F to 190°F).
Matt,
It does need to be done by an A-Series specialist, and would be worth seeing if your Marina block has been sleeved and whether it is too late as it's already at +0.060".
The head gasket I use is from MiniSpares, and is their part no. TAM1521. It has a thin section between cylinders 2 and 3, which is quite narrow after the 73.5mm bore, and the gasket should not overhang the bore.
For reasons nothing to do with head gasket, the actual time between changes has been a maximum of around 12,000 miles. After the first 3 years (10,000 miles) I stripped the engine to re-hone the bores, then after about another 12,000 miles I had some work done on the head to increase the CR to 10.4. In neither case did the head gasket look in need of replacement, but obviously was as part of the rebuild.
If you do go the 1380 bore route, make sure that you use a very basic 20W/50 oil to run the engine in. The problem I had when I bought the engine was that it had only ever been run on a fully synthetic oil from new, and the rings had never seated properly - oil consumption of 1 litre per 200 miles at best! After re-honing the bores, new rings for the Omega pistons and running in properly, the consumption now is around 1,000 per litre on full synthetic, which is very acceptable.
It decided to spew oil all over the motorway and sieze (a bearing spun and welded itself to the conrod and crank)
Sorry to hear your engine is worse than originally thought, Matt. If you're thinking of chucking the lot in the crusher I'll have the exhaust!! 
Think I would bundle a complete replacement lump in. The benefits of a few extra cc probably not worth the concerns. If it's gone oval at +60, what will it do if you go further?
