I have a 1968 350 that came in the car when I get it its a l48 motor I know there not a great motor to start I tore it down and it was rebuilt not too long ago it looks great it is bored 40 over I have a friend with a set of 305 heads I want to purchase a cam and a set of headers would the 305 heads be a improvement from the stock l48 heads im not interested in spending a ton of money to make the motor perfect just want something fun and reliable he wants 50$ for them so I figure its a good deal or I have a buddy with a set of 305 vortech heads for 100$ just looking for some advice on what way to go thanks in advance

 

Unless you are going to port those 305 heads with bigger 1.94" valves hold your money and buy some 350 L31 Vortec heads 062 or 906. You will really like these... Install on your 350 with a felpro.015" shim head gasket.. Get a performrr RPM vortec intake.
Gmpp blue LS3 valvesprings comp 787 conversion retainers.
Comp Xe 274h-10 cam
What is the head casting # on your heads?

305 heads in stock form (4416-601 etc ) flow less than your 350 heads do.. And the valves are smaller... If you want power gain you need to agressively home port the 305 heads for more port flow.. 1.94x 1.50 or 1.94x 160.
While this can be done with the effort the L31 vortec heads are flat out BETTER.

 

Some of the factory 68-70 L48 350 engines came with
a 64cc chamber high perf head. 291-041-186 etc (1.94-1.50 valves) Check your head casting numbers post here, before your buddies hijack your good heads for a lesser 305 head.

 

 

#882 heads are ~1975-78 76 cc smog heads-they can have 1.72 up to 2.02 intake valves. Similar to 993 and 624 heads

 

These are the early 882 head.. Heavyier casting than the late stuff but same lame performance.

Find a set of L31 vortec heads 062 or 906 castings.
The aftermarket version vortecs arevgreat also.
Enginequest EQ heads ProTopLine 906 etc
Anything with a hi perf 64 cc chamber and a highflow 170-185 cc port is good.
All 305 heads will need lots of porting and bigger valves rework to get the gain effect you are looking for.
If you are not going to do the full rework effort on a 305 head (081,4416,601) do not expect a good result.