Doesn't hurt. I installed an OEM shield after the intake cracked on my '78. The OEM shield is very thin and is not solid. My original shield was completely burned away. The most likely cause of the cracked manifold is a stuck damper in the exhaust manifold. Make sure the damper is free, or tie it open.
You don't need to replace the intake. You can have it welded. At least hang on to the old manifold as a spare or give it away to be repaired. My '78 has been running strong with a repaired intake for the past 8-10 years.