cams are same the 242 uses the older spring style retainer,button vs the bolt on thrust plate like on the 4.0. Grab a 4.0 block and head, swap in your 258 crank with 4.0 rods and stroker pistons like the Keith black 944's. Makes a solid 4.7 and won't break the bank. The 4.0 head kills the 258 head in flow. Don't be shy w the cam the strokers like more lift than many people believe. :-) good luck.
06-Corvette z51-6spd,b&b,K&N low miles.
77-Corvette Stingray 496 BBC/TH400 built 667hp+
00 WJ 4x4, 4.7 stroker, turbocharged,..lots more..
01 WJ 4x2 4.7v8 Limited (needs valve job)
90 Grand Wagoneer 401 Edelbrock Heads, Lunati .510/.527 FT Cam, Edelbrock RPM Air Gap, Holley HP 750, Thorley Headers, HEI, Electric Fan w Digital controller,4" lift 31x10.50 Goodyear Duratrac's on Pro-Comp Wheels,new interior, seats,seals,Alpine and JL full system, Remote HEI, Clifford 2 way with remote start,windows,tailgate.
96 Cherokee Country 4dr/2x2 White/Tan 3" Lift Sahara 18" Wheels 32.5"'s 99up head and intake- for sale soon!