two and a quarter petrol is a tough old motor; it's not that powerful, and not that ecconomical; but not much else will do everything an old four pot will, without some hassle somewhere along the line.
Realistically; in a 109, 55-60mph tis your top wack for speed. Towing, they will haul a good old weight...... just not very quickly.
I had 109 Diesil 2.25 which was even more gutless; but would trubdle along at 50 with 5 birth caravan behind happily enough; or pull builders traler etc.
Over drive is helpful, as it will let you 'split' the gears, especially 3rd & 4th and knock back the revs in top when you are on the level or without so much load; most useful on hills though with a load to give you a 2nd gear + and a 3rd gear +
Webber carb conversion is common; but I hear so many people have hassles with these things!
£75 buys an exchange new or recon zenith from Paddocks; and they dont give grief! Far more efficient use of money as far as I'm concerned!
Webbers dont give any more power; give barely noticeable ecconomy benefit, and a a bugger to set up; get them wrong, and that's dead easy to do with a webber, and you'll have less power, less ecconomy and more hassle.
Zeniths aint great; but you cant get them that far wrong; and they do work; if you have carb problems overrhaule the stock zenith, or get an exchange one; problem solved!
For winches; as said bigger the better; every-one wants electric Wwarn X900 designer icons on the front these days; but a fairy PTO capston winch is a damn good bit of kit and does the job! As does Fairy (aeroparts/superwinch) PTO drum winch.
Fairy drum is easier to use, and not so desired by the people that want that 'period' look, and can be found reasonably ecconomically.
You have choce of whether to drive off dog clutch from front pulley or via jackshaft from PTO on gearbox.
Jackshaft from PTO has benefits in that you can drive from the cab, but needs careful setting up to run the jackshaft forward, and to my mind benefits not so great as to warrant the complexity.
Straight of front pulley is simple, and I like things simple!
And, PTO winch, gives you all the power of the engine on the drum; warn 900 or whatever, 3.5hp electric motor? Hmmmmmm not for more than a minute or two matey, 'cos the alternator supplying it wont make that kind of power and a couple of optimas wont make up the difference for very long!
Old 2.25, has 75bhp, and will be making about 20 under 1500rpm! Even at tickover winch will have more power; so good value.
Going hyraulic; better than electric; but again a lot of complexity, that you can do without, unless you are REALLY going to work it that hard that often.
IF you want to go for an engine conversion; there are plenty of options; but evert time I've gone round this loop; only one that seems worth the doing off to me is the Rover V8 in conjunction with LPG.
Basically; as much power as you can realistically get, and as much ecconomy (from LPG); gives you biggest gains for the cost & effort of almost any other alternative; be it a tuned petrol a V6, or a deseasil power plant of some description. But a lot of effort, no little cost, and converting from standard gives you a hot-rod that will have some 'livability' issues; like servicing and reliability, and originality and resale value etc.
Springs; as said; you can have Standard, Standard Heavy Duty and get both with or without 'helper' leaves for heavy loads, and there is possibility of 'air assistors' between leaf and chassis with whatever spring you choose.
HD springs are very harsh though, so unless you are going to have a LOT of weight on the back most of the time, you might be better off with standard leaf plus helper, and or air assistor. Makes it a bit les rigid when no load on the back. As pick-up, lack of rear body makes unloaded rear axle weight quite light to begin with; and HD will often make back 'hop' becouse there simply isn't enough weight on the axle to make spoing move.
HD dampers however would be more useful, and in conjunction with standard = Helper spring probably be best starting place.
If any of that helps.