40-a-twins
If the "modern" gasket is the type with a ring of sealant around the gasket openings, do not use. Quite a few have had issues with short time failure, sometimes within a couple of hundred miles. I do not think the issue has been definitively identified, lots of personal experiences both pro and con. Some say correct installation procedures were not followed while others insist they followed procedure to the letter and the modern gasket quickly failed.
Some say the Head and Block were not prepared proper, flat and with the proper finish. But the graphtite and copper/copper clad seems to be more forgiving since it is extremely rare to hear of a short term failure of these gaskets. Some say to break in the modern gasket for a few thousand miles and a few re-torques using water coolant, then switch to antifreeze if antifreeze is desired.
Graphtite works well, but it can be difficult to remove the material from the block/head after they have been on the motor for a time. Graphtite do not need as many re-torques after installation and over longer periods of time - seem to hold their torque better. Copper is a lot easier to remove, but requires a few torques and usually best re-torqued occasionally (once a year is enough). When re-torquing it is best to drain the coolant down below head level to prevent coolant seepage.
Here are more strings on the subject of head gaskets.
https://www.fordbarn.com/forum/showt...te+head+gasket
https://www.fordbarn.com/forum/showthread.php?t=290073
After reading all this, seems the general consensus is the copper/copper clad gasket is the safest bet, just be sure to follw recommended installation, head and block preparation, torquing and re-torque intervals on it.