Just bought a 68 valiant with a big block with a 727. Will a transmission shield fit with a stock floor? Does any brand fit better than the others? Thanks

I would buy a blanket, and have used one in my old pump as Duster with a 400 stroker motor, not a shield.
I had bought a SFI certed carbon fiber shield and ended up not using it due to my motor being slid back around one inch from the stock engine location, I slotted the tranny mount to get the motor and tranny where I wanted them to be

If you really want protection, get a blanket. I've seen two cases where a shield did almost nothing.

I have a 1975 Duster with a 440 and 727. Car has stock K frame with motor mounts. I run a CSR shield. The only thing I had to do to make it fit was beat the firewall/floorpan seam flat as it hit. I did drill access holes for the bell bolts to make life easier.

Yep seen a shield fail twice, buy a blanket. Better yet buy the blow proof drum. It has been discussed on here before.

How fast?? IIRC the CSR shield provides both the trans and flywheel protection for the 9.99 and faster rule….blanket does not. I also agree that a blanket will absorb energy better than the CSR shield.

Blankets work well. But they are bulky and hold heat. They also can collect fluid if you have leaks. If it's a dedicated racecar the best thing I ever did was open up the tunnel for clearance. Then you can run an aluminum shield. It's not that hard to do.
Doug

A local racer exploded a stock drum 727 with a CSR carbon shield in his 1963 Dodge 330 sedan, it ruined the stock floorboard and tranny tunnel as well as broke some bones in his right foot,

No, shield will not fit a stock floor. You'll have to get under there with a hammer and move some metal around before a shield will fit. I tried to put a shield on the 727 under my Duster and finally gave up. It was a street car on street tires so I sold the shield to a racer and stopped beating on the floor.

I prefer a 1 piece shield rather than having to run a blanket and separate flex plate shield, almost always you have to modify the firewall / floor seam to get them to fit. I agree that a blanket would work better in the event of any explosive failure but I also try to minimise that risk as well.
You can re-tag and re-cert a shield as long as they are in good condition and they are a lot easier to clean. If a blanket has any oil soak or contamination, it won't re-cert.

Victory NSS racer almost lost his foot due to explosion with a shield. The gas pedal was "C" shaped and did more than anything. The shield completely turned into a ball of yellow (kevlar) yarn and disappeared. After seeing that, it is certainly my opinion that the shield did NOTIHNG.

Wrap both ends of the blanket around the torsion bars. You probably have to make a bracket off the dust cover bolt to hold the blanket off the headers on the drivers side. That's all you have to do.

Check everyone manufacturer that make them :scope, buy the one you like best
I bought a Lofgren, I think it was, for my pump gas Duster years ago