I have Roush 427R-095. It's gone about 8,000 miles now with no problems. If I bought another 427R I'd request the same spec build again. The 427Rs seem to have evolved over time. I change the
oil about every 500 miles or so. I fart around 99% of the time the engine is running, but for the other 1% of time I changed the rev limit to 7000 rpm, put on a 1000ish cfm mechanical secondary Pro-Systems carb(flawless operation, light switch, pulls like mother), changed headers and side pipes. I've got the single plane intake. The changes added 70 or 80 wheel HP.
From what I understand the Tremec transmission is to be driven easy at lower rpm for about 500 miles with easy shifts for proper break in. It will shift like butter after the break in. I did have the two bolts that hold the shifter come loose. This allows the shift lever to move while the actual transmission shifter doesn't for part of the forward and rearward movement your hand makes. For the 2 to 3 shift in particular it can cause a missed shift. It's an easy fix if you seem to have a sloppy shifter. Just pull the boot and tighten the bolts. I put on a light weight flywheel and SPEC stage 3 clutch. It works ok.