time for my $0.02.
In my opinion the "L" series comes out with the gold, as cheap as they are, ( 200 bux with gearbox) Are also quite easy to install.
there nothing compared to the degree of Difficulty which is invovled with the "CA" conversion. The "L" series gear box will fit the standard tunnel with some "massaging" but is easily fitted with an upgraded tunnel.
then theres the cross member, The L18 sump is at the wrong end, so the sump has to be pulled of a L20b with the right configuration sump and bolt back onto the L18, then u need to remanufacture the mounts for the L18 block.
The L18 with a single side draught webber, decent cam, port n polish, and a head shave to up compression willl be a quik ol' datsun 1200.

. And it would be a cheap option to boot! In NSW the limits for a datsun 1200 are:
2 Litre Natrually Aspirated.
1.8 Force fed.
So as you can see getting one registered will be quite simple indeed because the L18 ( 1.8 litre) fits in the requirements.
The A series ARE great Bang for Buck.
they go in easy are cheap and are reliable.
They have got themselves a reputation that is gold. there a great little motor.
but it comes down to, theres not replacement for displacement, and the L18 wins every time.
Go the L series they go heeps harder than an A