I would investigate building a "replica" instead of "car from scratch"

rules for replicas are far more favorable, and there's not much test for how accurate your replica is

Good point, when your government has restrictions on engine size. E.g. 2.0 liter is usually the limit in Australia. An ICV (Individually Contructed Vehicle) is one way to exceed the limit, for example put your 1200 body on a frame chassis that is designed for a larger engine.

What kind of replica vehicle?

is it a clubbie type vehicle eg. westfield, caterham or other?

How about a factory rwd 2.5 v6, heaps of aftermarket support for the VQ

VQ25HR
The 2.5 L VQ25HR (for "High Revolution" or "High Response") is only offered on longitudinally-mounted engine vehicles which tend to be rear wheel drive or all-wheel drive. Bore and stroke are 85 mm and 73.3 mm, with a compression ratio of 10.3:1. It produces 235 PS (173 kW; 232 hp) @6,800 rpm and 194 lb·ft (263 N·m) @4,800 rpm. It has dual CVTC for both intake and exhaust, microfinished camshafts and a redline of 7,500 rpm.

It is fitted to the following vehicles:

2006–present Nissan Skyline V6 250GT Sedan - 235 PS (173 kW; 232 hp)
2006–present Nissan Fuga 250GT - 223 PS (164 kW; 220 hp)
2006–present Infiniti M V6 M25 Sedan - 222 hp (166 kW)
2010–present Infiniti EX J50 EX25 Crossover SUV - 235 PS (173 kW; 232 hp)
2011–2012 Infiniti G V6 G25 Sedan - 218 hp (163 kW)
2012–present Mitsubishi Proudia 250 VIP - 223 PS (164 kW; 220 hp)

Im sure with good springs, redline limiter removed 8500rpm
vq35 or vq40 itbs it will be a rocket with this stroke