oh goodness gravy, i "guten tag, wie gehts" one guy and they're coming out of the woodwork. :waving:
your "375" is a factory Gross Torque rating and is only loosely related to the engine size, which in your case is the high compression, 4 venturi carb, 340 cubic inch Buick small block engine with 260 Horse Power.
"Gross" Power and Torque ratings do not reflect "as installed" performance as modern SAE Net or Euro standards do, they were made from the flywheel with open headers, no water pump or accessory belts, no transmission, with a blueprinted engine ( hand built exact specifications for deck, compression, etc, rather than the sloppy stuff that came off the production line ) and the highest octane fuel available. comparing Gross numbers to SAE Net ratings usually shows the 1960s era method to overstate by about a 1/3. so your engine is probably more like 190 HP right now in good running condition.
the 340ci was only in production for two years ( 1966 and 1967 ) and it is the only 'Rover style' Buick small block with it's deck height. what this means, is that your intake is the best one you're going to get unless you hand build something. some other parts may be very difficult to find.
as you may have guessed from the previous paragraph, the Buick small block family is the basis of the Land Rover v8 which was in production from 1965-2004. the Rover engines are metric variants of the 1961-63 215 cubic inch / 3.5 liter aluminum block engine which was Buick's 1st generation of the small block. you will be able to find many Rover parts which will fit with little or no modification such as timing covers and valve covers. Rover pistons are likely to be a bit .... inadequate.
any classic Land Rover mechanic should have little trouble finding his way around this motor. neoprene front and rear crankshaft seals are available, so make sure to change out the rope seals.
the 1966 Chassis Manual is here and should cover pretty much every aspect of your car:
https://www.teambuick.com/reference/library/66_chassis/index.php
the primary Buick aftermarket vendor is here, they ship overseas:
www.TAPerformance.com
D&D has been playing with Rovers and Buick small blocks for decades and sell many interesting parts which may be possible to use or modify for your engine:
www.AluminumV8.com
the British V8 forums can be a great source of knowledge and parts for you:
http://forum.britishv8.org/
guten abend und guten nacht.
