I am putting together a 440 six pack to be mounted in my 71 Challenger 4 speed. I have started from a bare block, had some TRW 2295 pistons, a set of newly rebuilt 80 cc heads, six pack rods, balancer and flywheel, and a Comp Cam 274 cam. What kind of valve springs and pushrod shall I use? I don't have an idea about the valve springs already mounted in the heads, they were purchased many years ago off ebay. Also, shall I use 3/8 or 5/16 pushrods? Rocker arms are the stock units. I plan on using the original valve covers, if this matters.
Any suggestion about pushrods and valve springs. Living in Italy makes everything more difficult. Thank you for the help

I would shoot for between 120 to 160 lbs. pressure on the seats and from 325 lbs. to 375 lbs. at max lift, check the pushrod preload on the lifter cups and shoot for between .010 to .030 between the bottom of retainer and the top of pushrod cup
Good luck, you can do this

Found this specification card from the seller....valve spring pressure seems ok

watch "pushrod geometry for engines" on www.youtube.com for correctly sizing pushrod length. the one from Straub industries with the yellow rocker arm

I'd call Summit and order new comp springs and push rods. Just tell them what cam you have. They can hook you up. It won't be too bad. Summit may even have both under their logo, they are made by Comp, like their cams.

Your motor will be at or over 11:1 compression ratio. Will you running racing fuel? It will probably need 102 to 105 RM/2 octane fuel, or 110+ R octane.

I am lowering the dome on the pistons by a couple of millimeters to lower compression, and will use higher head gaskets. My english is not too great, so talking on the phone is not my first choice....
By looking at the shop that did the heads, seems seat pressure is correct.

Make sure the motor starts right away, less than 5 complete crankshaft revolutions, and runs at or above 1500 RPM for 30 minutes to break in the cam and lifters Set the ignition timing while it is running and make sure it doesn't get to hot while breaking in the cam and lifters, I'll shut them off if they start to get hotter than 200F and let them cool down to 160F or less and then complete the break in time. Do that as many times as it takes
After the cam and lifters are broken in change the oil and filter and cut the filter open to look for debris in the pleats, all new motors make debris but it shouldn't be a bunch I normally see debris in the oil filter up to 3 changes and then they stay clean, engine assembly is like brain surgery, it is absolutely impossible to keep it to clean. I try like hell to keep them as clean as I can, I found a eye lash in one filter a long time ago
I've have and use a clean room to assemble my motors since 1975.
Clean, clean, clean and clean them some more
Make sure to use a good high quality oil with zinc in it or a zinc additive to help protect the cam and lifters
What is the quality of the fuel you will use in this motor?

bar the engine over before you install the intake and make sure all the lifters rotate in their bores !
if they don't, the cam will go flat in no time, and you will be taking the engine out for a rebuild to insure there are no metal particles left inside the block passages and the bearings are not scored from said particles.
swap the lifters around in the bores, or try a different set of lifters, whatever it takes so they rotate on the cam lobes.
unless you are using a roller cam of course.
then follow cab's instructions.

Thank you for the advice....
Any idea about pushrods size?

Stock size is 5/16 ball and ball, you don't need any more than stock with those valve spring pressures