Ya i asked the same question couple months ago. The 243 heads will definitely show major gains over the 241's. Also when you get them ported thats when you will see and awesome gain.
I would actually look into TSP bc they have the PRC stage 1 LS6 heads for only $950 and they come already ported and with a competition valve job.
Save the money and go with the PRC's
1999 Trans Am. 347 build. and a lil nitrous.
2008 Yamaha FZ1 10.0 @ 135
93 LQ4 Coupe in the works.