Studs, you mean head bolts?
Would the motor run lean with 5x11's? Or just not enough fuel to reach full potential?
Need to figure out the oil usage, could it be because it is a huffing and a puffing a bit under full pedal?
I mean studs unless you have the ability to make the custom washers required for the socket-head bolts. They all need a chamfer on the ID and the ones that go between the valve covers need to be turned down so as not to cut the gaskets. Studs will help hold the gasket better than the socket caps, depends on how much of a gamble you want to take with blowing the gasket.
Diesels don't have the same lean/rich sensitivity that gas engines do. Gasoline, spends all it's time in normal operation between roughly 11.5 and 18:1. Leaner than 18:1, you start blowing holes in pistons and experience sporadic combustion. Richer than 11.5:1, and you start getting black smoke and retarded combustion. A clean-running diesel is always running lean. Off hand, I'm not sure what your "just driving around" AFR would be, probably between 30:1 and 50:1 I would guess. Stoich for a diesel is ~14.6:1, but visible emissions begin around 19:1. Basically, you will start hazing before you reach stoich. Diesel will make the best power between 14:1 and 10:1, but going richer than that will start to retard combustion. I have an AFR meter that I'm going to integrate into the datalogging setup I'll be running when my truck is back together.
A 5x11 will not give you any driveability issues, you'll just be limited to essentially the same horsepower a K27 can support all on it's lonesome. The 5x11s may not fuel hard enough to spool the 369. I'd argue there's almost no point installing the 369 with those injectors.
I'm not sure what your oil usage is about, I would check the obvious sources one by one. It would be a good idea to replace the valve stem seals when you do the valve springs. Mine were done when I tore down at 334k.
A 60 lb spring is more like 150 lbs of seat pressure. Thats good to know. It seemed way to close to the blow open point. K27/369 looks like a very fun setup. Wish I read up on he k27 before getting the super b. Looks like the smaller tubine would contribute nicely to quick spool.
"60lb" springs are a factory part for a 370 Marine engine. They got the name they have because one of the exhaust brake manufacturers started selling them as an upgrade, advertised as allowing an increase to 60psi of backpressure from the brake, where the stock springs could only handle about 30.
I ran a 57/65/.8 S300G on mine for a while before I took it apart last fall. This is what the Super B is based on, it was hands down the worst turbo I've ever had on my truck.