Use the standard mechanical pump - it's low down and has no problems in hot weather with fuel starvation due to vapourisation in the lift pipe to the electric pump.
Depends on how tuned it is. My 1380 Ital engine under full throttle uses more fuel than the standard pump(s) can supply (hard to believe I know) so I had to go for a rear mounted FACET fuel pump which ups the pressure to about 5psi which is then dropped to around 2psi by a filter/regulator mounted on the bulkhead (where the old SU pump was).
BUT If the engine in question was in pretty standard tune then I would agree with bmcecosse and use the mechanical pump as it eliminates the vapourisation problem.
I would agree with using the mechanical pump, unless you fit an LCB exhaust manifold where you will find the front branch passes precariously close to the pump on the side of the block. At that point I reverted to standard SU electric pump which worked fine.
Obviously if you're using the standard cast iron manifold its not a problem and its up to you. If you've got a good SU pump on the car, it saves messing about altering the pipework, but if you need to buy a new one, or have had problems, the mechanical pump rarely gives trouble. Only had to change one once (on a Marina) because it was seeping fuel from between the top and bottom halves of the castings.
cheers
Iain
Fairmile Restorations.
'49 MM, '53 convertible, '55 van, and a '64 van.
Marina p.u., '56 Morris Isis Traveller, a '59 Morris JB van, a'66 J4 van, a '54 Land Rover, Land Rover 130, Renault 5, '36Railton, '35 Hudson, a Mk1 Transit and a Sherpa Camper...
A car can be restored at any time, but is only original once!