My experience was with fitting a RR V8 into a SWB Series III so pick from
this what you will........

I did away with the battery tray altogether and relocated the battery to
under the LH front seat.  To get it in there I also did away with the
toolbox thingy under the seat, cut the top off an old fuel tank and bolted
that up onto the outriggers in its place.  You'd need to have a military
spec chassis to do that though (they have the extra fuel tank outriggers on
the left-hand side) or weld on either a tank outrigger or something else
that you can hang the tank/battery box on.  I didn't think the standard
toolbox thingy was deep enough for a battery.

The gearbox in my V8 88" sits in its usual place with modified engine mounts
to put the donkey where it needs to be.  I haven't had to cut any holes in
the bulkhead to be able to get at the plugs (although I admit that the rear
ones, particularly on the left side, are a bit tight to get to).  Of course,
the bulkhead and tunnel did have to be modified.  IIRC both footwells had to
be shrunk slightly and the centre "bulge" deepened and extended.  The heater
matrix has to be moved over too to avoid fouling the inlet elbows (assuming
carburettor V8 like mine), which in turn means you have to move the blower
motor over a bit and also means you have to blank off half the bulkhead
hole.  Mine still puts out plenty of heat though, and the cab is like toast
once the engine and exhaust pipes get warm anyway!

I had to move my alternator from the left side to the right side (the engine
came out of a Range Rover) and there was a bit of a faff finding a suitable
mounting bracket.  My donor didn't have air-con so maybe the air-con pump
mounting bracket would be suitable (my alt now sits where the air-con pump
would be).

Add a remote oil filter and, if you're using the standard series radiator
like I have, an electric radiator fan.  I could have moved the radiator
forward and used the viscous fan, but I wanted to retain the Series III
front.  For the exhaust I had to extend the down-pipes just after the
manifold connection but the manifolds themselves certainly don't foul
anything.

Steve

When we put a V8 in our series 2. I kept the battery in the engine
compartment in the original place. The alternator we moved from the left (as
if sitting in drivers seat) to the right and made up a new shorter bracket
so it cleared the battery. I didnt want the battery under the seat as I
wanted the space for tools etc.
In our V8 90 I would love the battery in the engine bay but I cant see where
it would fit.
Off the shelf exhaust for 88" with a V8 from Jake Wright

Richard