Yep ...you have to change the heads cause they are a "hemi" design with HUGE chambers..like 91cc. OR have the them welded up and re-machined by someone like SBC..and thats $1000.00.
Start adding up the parts , including the labor, and dont forget the $300.00 for the timken update on your cases. Cams , heads, cylinders, bore the cases to fit the cylinders, and you end up with used cylinders, CVO cams no one wants, CVO heads ...E-Bay??
When to get near that $6000.00 mark that 120 Jims sure starts to look better and better..It's really bullet proof for any kind of street use..and you have your complete stock motor to stick back in when you sell.
The Jims has beefy cases, timken bearings on both sides, 4340 rods, roller rockers, springs that will go to .700 lift, 264 cams, adjustible pushrods,heads.forged pistons.....all the good sh*t
A Jims 120 "A" motor costs the dealer @ 6100.00. Tell them "low Gross is better than no gross" and offer them 6500.00 and let them make some money on the install.
Or ...pistons,heads and cams for your 103 ...can make some really good power for way less money....the 113 just doesnt make $$$$$$ sense to me.
But hey..just throwin out some ideas.