When I had my Lancer repowered a few seasons ago I went with a MERC 260HP 5.7 MIE. Even though the Lancer has a Volvo I/O it does not use an I/O engine, it uses a stock bobtail.
I decided on this engine because its manifolds are FWC, not just the block and it had a 2bbl carb. Why not a FI or TBI engine you might ask. Just being a bit a dinosauer. I've gotten home on other boats of mine with malfunctioning carbs that I've taken apart and cleaned more than once. On a FI engine...it's "Call Capt Shawn!". I already had one episode with ethanol that had the engine been FI or TB would have been EXPENSIVE. All it cost me was a carb gasket.

For me, the other big advanage of a FWC engine is the operating temp. RWC engines run in the 130-140 degree range to prevent deposits. FWC engines run in the 160-180 range. This higher temerature give one two advantges: 1) Oil runs hotter and tends to "burn off" moisture and have a less tendancy to sludge out.
2) The higher operating temps give you better gas mileage.
When the GMC engineers designed the block and pistons and internal clearances, they designed for temps close to 190/200 degrees. As engine temps rise, clearances change. At 130-140 the engine is not running at the design point.

One other reason for choosing the MERC is that the setup in the Lancer (admittedly rare) allows the use of an engine with a starter in the "up" position, greatly prolonging starter life.

An lastly, the other reason I picked MERC is that I have a bug in my ear about VOLVO. Some years ago a friend had a boat built that had factory installed VOLVO gas engines. It never ran quite right. He complained many mnay times and had repeated problems. At one point he had a Volvo rep come and look at the engine/installation and the rep said.."looks OK to me". The engines finally failed less than two weeks after the warranty expired. When my friend tried to get the engines fixed under the warranty, he got turned down. He escallated it up to the VP level at Volvo and got a letter in return that Volvo would not fix the engines under the warranty as the engines "had been improperly installed"... This despite the fact that the engines were installed by a Volvo certified manufacturer and had been inspected by a Volvo tech rep.
While Volvo of Sweded may be a great company, if you have a new Volvo these days you are dealing with Volvo USA... an acorn that apparently has falled far from the tree, so to speak.