E30 is a high compression, small(er) port and small(er) valve head - designed for good low down torque and economy.
swapping to a larger valve head like an E31 is hard due to the Zed boys pushing the prices up (Craig...
) and the E88 is a lower compression, later model head from memory - off the R30.
you could always use any plethora of L26/L28 head options like N series, P series etc but if you want to keep it TRULY L24 the E series heads are all you can use from an originality point of view.
my advice for a stylish and simple daily is keep the E30 head, find some dome top twin SUs and manifold (i have 1.5in SUs that i think the sale has fallen thru on if you need them - i have no deposit anyways), use a shorty factory cast exhaust manifold (you may already have one - i have one if you don;t that you can have for nothing bar freight cost) with a good 2in exhaust and a mild grind cam (i think crow still do a 28/68 for the L series).
if you can't get twin SUs, have a new 32/36DGV or 34ADM weber jetted to suit.
these mods will make it shine and give you a fair but more power for about $1200 outlay using quality gear and a new carb / rebuilt SUs.
if the whole engine needs attention, rebuilds are cheap but make sure you go to a quality workshop.
if you can put your location in your profile it would help us to help you more accurately.