So far Nothing has gone wrong with the car, Know that I can afford it, I always thought this car was under powered for its preformance. It can power brake, but I think it can do better. I have bought a 455 cubic inch big block motor for it, also I have had a custom 700R4 made to fit this motor and mount up nicely to this mounts.
If you want sound out of a 305 I would recomend headers and 3 inch exhaust with no converts or mufflers.
I know the 455. It'll make mincemeat out of the 700R4 in short order. Use a TH-400 instead.
Depending on the year of the 700r4 transmission will determine if the 455 makes mince meat of it. A stock 700r4 tranny from 82 to 86 will be made mince meat with anything bigger than a stock 350 v8. 87 and later 700r4 stock trannys will stand up to a stock big block 455 under normal use and not racing everyday. A properly rebuilt and strengthened 700r4 can stand up to 500 horsepower and a properly rebuilt and strenthened turbo 400 tranny can take upto a 1000 hp. Hope that helps.
I agree with the no muffs/cats comment... I had an 82 Delta with the 307, that thing was definitely the most Irate sounding straight pipe car I've ever heard! Look on youtube... I think there's one on there with straight exhaust.. Definitely not bad.