All L series will need clearancing but best is the L16 which will fit but an L20 wont as discussed before unless you run a giant power bulge as dodge said and then the handling will suck big time as the thing will sit way to high and its much heavier than the other smaller Ls specially if the latter L20 is used with the extra webbing. V6 is a different story as even a chev v8 has been in a 1000 (iron chev 250kg plus or v6 alloy nissan vg30 160kg plus) but they arent as high as the tall mother L20. Trust me a good a14/15 will scare you if well sorted otherwise an L16 with L18 crank or l13 with clearanced l16 crank will be possibly a lighter engine with the balls of the l16 or even the L18 crank if the L16/l18 blocks are the same height as previously discussed with Harry but best ask him or feral. The L13 engine has bigger everything and the oversquare design with L16/l18 crank will scare you back to driving corollas.
Also the L series engine can take a twin plug crossflow head design from the Z18/T engine for extra flow and performance.