Yeh, guys the L series motors are brilliant, you would know after owning one.
I have an L series motr in my Skyline GTX, in my previous 280zx and 240z.

For a 1200, I would suggest putting on a hotted up A series motor, cause this would be less time consuming and cheaper.
However if you have time and money, go for a L series.
These motors, personally, I have found to be much more long lasting compared to an A12, if you drive it hard, and gearboxes can take a lot more beating.
Believe me, theres nothing like the sound of a L series grunt, especially with a turbo strapped on. MAJOR POWER.

Guys, no offense, but L series motor can definatly take a beating compared to A series motors.
Bigger is not necessarily better, but in this case, it is.

Although I love the L series, I wouldnt put one on my 1200, cause I wouldnt want to disturb the originality of my Datto much.
I love my Datto for what it is.
If I had to, I would go A14