teg LS Q
 

i have a 90 civic with a B18a in it, now i may be able to get a b18b head or cams for free and ive heard the only thing that makes the B more powerfull than the A is the head or cams. i dont have the cash for a vtec head yet but i still wanna tinker with the LS. is this worthwhile? labour is not an issue here

The question here is, are you going to swap a vtec head onto your ls block eventually?
I mean, hell if your getting a free b18b head, and labour is not a problem, and you feel the need to tinker, go ahead. There is no cost, and you can play around with your engine.
BUT if you really think your going to get a vtec head, why go through all the trouble of swapping heads, and in a few months do the same thing over again. Unless you really enjoy it.
If you can get the head for free, take it, then resell it, and use the money towards something you will need with a vtec head.