want to put a 440 in my dart

hey guys iam new to this site. i have a few questions about swapping a 77 motorhome 440 with a 727 trans. i know there is lower compression. is it worth the time and effort. i planned on building the motor getting a set of flat top pistons. but i wanted to know if the block is the same and if i can still use the stock crank and rods.i plan on getting a set of 906 heads and putting them on. will those bolt on? i plan on rebuilding the tranny and adding a shift kit and getting a different torque converter.will that bolt in? the car is a slant 6 car with a 904 auto.iam gonna buy the shumacher big block kit will that work with the motor i have i bought a complete motor and tranny running for 500 i want to know if i wasted my money please help i dont want to buy anything else until i know.or can i use the stock heads and have them built. thanks for the help