stock 1969 318 rebuild. Purchased new ARP connecting rod bolts. I tried putting the bolts in the frezer and heating the rods to 250 in the oven. Could not get the bolts to seat by hammering them in. They went in about 2/3 of the way. I tried just running the nuts to pull the bolt through on one rod. One went through ok and the other doesn't seem to want to go. I did not want to lean on it too much. I abandoned this idea as I think it may stress the bolt out. Do the bolts have to be pressed in by a machine shop ?

Not only do they need to be pressed in, you will also need to resize the big end after that.

X2

Any time you disturb the big end of a rod by changing or removing those type press in bolts you should always have it check for roundness and I.D. size

take rods and bolts to machine shop. they will cut the rod and cap. install bolts, torque them then rehone bores to proper size.