Lucas Prince of darkness. For 914 driver

For some reason I can't respond to your question.  This is my work around.  
    Lucas gets a bad rap when the truth is they make some good durable stuff. For example their fuel pump is the butt of many jokes. While   the truth is they need regular cleaning of the points and they will last for decades. Since it takes about 2-3 minutes to do, I fail to understand. 
   Well,  yes I do. Mechanics make an hourly rate and a bonus on parts they sell.  If they replace a part they can earn 10-20 times what it costs to do the job properly in the first place.  
      When Sir William was running the Jaguar factory, his employees understood  how tight the budget was and took pride in doing the job to the best of their ability. 
When Jaguar was taken over by BLMH  that connection was lost and employees  were treated like a cost item on a budget sheet. 
   So from the late 1970's through the mid 1980's  labor felt it was their duty to work as slow as possible. While some went so far as to Sabotage   the cars. For example only lightly tightening wires. 
    Once John  Egan  brought Jaguar back from BLMH  he reconnected with employees and once again they took pride and  then crease in sales reflected it.  
During BLMH ownership Jaguar was losing as much as £50 million a year. 
     Short answer Avoid late. 70's to late 80's cars if possible.  But there are lots of cars of that era in the junkyards with few buyers so good used parts are really decently priced. Often a loose wire would cause parts to be replaced that were still working nicely. ( remember what I said about how mechanics are paid?) 

Lucas parts made back in the day, especially NOS, are highly sought after.  Parts made after the sourcing changed to the Orient have a horrible reputation.   And I agree with frenchy about the bad old BLMH days.

You didn't ask but given the choice of the two engines you would do well to take the Jag Six  

    There are plenty of sources for parts  for it.  ( don't go to the Jag dealers)  that same basic engine was designed During WW2 and in production until 1987. In a dozen different iterations.   It's plenty powerful because of its torque. Caused by the long stroke. (4.17) but dont rev it past the 5500 RPM redline if you want it to last.   
    Like all Jaguar engines it's well built.   But it's an old design. 20W50 oil is required.   Either accept a little leakage or get really anal about dealing with leaks.  Oil is cheap. A baking tray or two will keep the floor clean.  
      The transmission though while long lasting is an old  design. It's a Borg Warner.   Originally used in Oldsmobile's, Packards,  and Studebaker, Johns cars has a kit to convert to a Modern G M transmission.   You  might be lucky and get the manual transmission.  That is a great gearbox. I raced for decades with one I pulled from a rusty Junker  and never once had any maintenance done other than change the oil.  I even had a spare that went with the car.  They are stout. 
    The rear end is a Dana. Most are IRS do not attempt to do brake work under the car. You will hate yourself. Spend 45 minutes pulling it and then brake work is a breeze. Front brakes are typical.  
        Suspension work is pretty straight forward but it helps if someone will show you the short cuts and techniques.  
    Number one.  Look for rust. There are completely rust free examples out there. More than you'd expect, really.  But once the dreaded tin worm gets chewing on the steel forget it. It's worse than a chain smoking coal miner for how fast the cancer spreads. It's not just the rocker panels, the cowl and windshield posts fall victim along with the rear window area.  And gas filler.  
 

Thanks Frenchy!  On one of them the brakes and  suspension has been gone through.  50W isn't a concern, you know I have a 914 right?    =~ )