I have an orginal 1973 Chevy truck with a 454 2 bolt main, steel crank. Would 781 heads come on something like this?

Could have. Pull a valve cover to be sure.

336781.....73-85...oval...OPEN...454, 118cc chamber, 256/114cc ports

The one I had did. I think mine was a 75.

What size valves did the 781s come with?

What size valves did the 781s come with?

they either 781's or 049's I had a 73 witg 049's

781's came stock with 2.06, 1.72 valves

Just a rule of thumb, Most your 70's 454's will come with either the 781's or 049's unless it's a early rectangle port motor. Once you get to 1980 you start seeing way more of the 454's with peanut port heads. I won't list actual years, this is just a rule of thumb when I am looking to get a 454 core motor.

My 496 started out as a '75 "TSC" 454 BB C/K 20/30 P/U engine w/ good -781's on it.

pdq67

I see quite a lot of posts with the 049's and the 781's in them, but I am yet to see many post about 290's ?

I realise they are Closed chamber, but apart from that are they a reasonable head ?

Sure, the closed chamber oval port heads are good...just the 781 and 049 start out a little better. some tune-up in the port and under the valve closed chamber ovals run well.
Ask 10.4/124 Tweety TC member FourEightyNine

290s are just like the earlier 063s that I run....but IIRC, it takes the tapered seat plugs

Do most guy that are build motors and want to stay with cast heads look for the 781? What cast head it the most sought after and why? JP