Straight six sounds better, has more power but weighs more. Four cylinder donor would've been lighter, cheaper and easier to find though. On balance, for me, it had to be a six for the sheer aural delight when double de-clutching down changes. Having said that, the old Triumph fours sound better than pretty much any modern sports car through a stainless exhaust anyway so whatever you choose to base your Sammio on it's going to sound
good.
Don't quote me on this, but I'm sure you could reposition the fuel tank on the Spitfire chassis to behind the rear axle to free up some luggage space in similar fashion to the way some of us Spyder builders have. You just need to teach yourself welding if you don't already have that skill.
Now, if you're really finding it difficult to decide then let fate intervene and buy the first
great donor that pops out of the woodwork, whatever it happens to be. And I have to say that Chap68's offer of a Vitesse with a 'blasted chassis thrown in looks like a pretty good deal to me...
d
Anyway, good luck making a decision, but you're already trying to choose between the best value kit car packages available - one Sammio or another.